Scientific Inquiry and Practices

The Nature of Science means learning how scientists find out about the world. Science is not just a list of facts. Science is a careful way of asking questions, making observations, testing ideas, and learning from evidence.

When scientists study something, they want to know what is true about the natural world. The natural world includes things like plants, animals, rocks, weather, water, and space.

Scientists do not just guess. They use what they can observe, measure, and record. Then they use that information to explain what they learned.

Science helps us answer questions like:

• What do plants need to grow?
• Why do shadows change?
• What happens when ice melts?
• Which materials float or sink?

1. Science begins with questions

Science often starts when someone notices something and wonders about it. A scientist might ask, “Why do some plants grow taller than others?” or “What kind of surface makes a toy car roll fastest?”

Good science questions are about things we can observe or test. For example, “Do plants grow better in sunlight or in shade?” is a science question because we can test it.

A question like “Which flower is the prettiest?” is not a science question because different people may have different opinions. Science works best with questions that can be answered with evidence.

2. Scientists observe carefully

An observation is something we notice using our senses or simple tools. We may use our eyes, ears, nose, or hands. We may also use tools like rulers, timers, magnifying glasses, or thermometers.

Careful observations are important in science. If we rush or do not pay attention, we may miss something important.

Examples of observations:

• The plant has 4 leaves.
• The rock feels smooth.
• The water is colder today.
• The toy car rolled 20 centimeters.

3. Scientists gather evidence

Evidence is information that helps answer a question. In science, evidence comes from observations, measurements, and tests.

For example, if we want to know which paper towel absorbs the most water, we do not just pick one we like. We test each kind and record what happens. The results become our evidence.

Evidence is important because it helps scientists make fair decisions. It helps them explain why they think something is true.

4. Scientists test ideas

Sometimes scientists have an idea they want to check. They can do an investigation or an experiment. This means they follow steps to test their question.

In a fair test, scientists try to change one thing at a time. That helps them see what caused the result.

For example, if we want to know whether sunlight helps a plant grow, we should keep the kind of plant, the amount of water, and the soil the same. Then we change only the amount of sunlight.

5. Scientists record what happens

Scientists write down what they see and measure. They may use notebooks, charts, tables, drawings, or pictures.

Recording information is important because people can forget details. Good records help scientists look back at what happened.

Here are some ways scientists record information:

• Writing notes
• Drawing pictures
• Making a chart
• Counting and measuring

6. Scientists look for patterns

A pattern is something that happens in a repeated or understandable way. Scientists look for patterns in their evidence.

For example, a student might notice that a plant gets taller each week. That is a pattern. Another student might see that objects made of metal sink more often than objects made of foam. That can also be a pattern.

Patterns help scientists make explanations about what is happening.

7. Scientists explain their results

After gathering evidence, scientists make an explanation. They answer the question by using what they observed.

A good science explanation includes:

• The question
• What was observed or tested
• What the evidence showed
• What conclusion makes sense from the evidence

For example, a student might say, “The plant in sunlight grew taller than the plant in shade. This evidence shows that sunlight helped the plant grow more.”

8. Science ideas can change with new evidence

Science is strong because people are willing to learn more. Sometimes scientists find new evidence. When that happens, they may improve or change their explanations.

This does not mean science is bad. It means science is honest and keeps working to get better answers.

For example, if students first think that all heavy things sink, they may later discover that some heavy boats float. New observations help them improve their thinking.

9. Scientists share what they learn

Scientists talk and write about their results so others can learn from them. They may share with classmates, teachers, or other scientists.

When people share science ideas, others can try the same investigation and see if they get similar results. This helps make science stronger.

10. Scientists work safely and honestly

Science should be done safely. Students and scientists follow directions, use tools carefully, and protect themselves and others.

Science should also be done honestly. That means writing what really happened, even if the result was not what was expected.

Good scientists do not make up answers. They let the evidence guide them.

Main ideas to remember

• Science is a way to learn about the natural world.
• Science starts with questions we can observe or test.
• Scientists gather evidence by observing, measuring, and investigating.
• Scientists use evidence to explain their results.
• Science ideas can improve when new evidence is found.
• Scientists share their learning and work safely and honestly.

Worked Example 1: Observing a plant

Question: What do I notice about my classroom plant?

Observations:

• It has 5 green leaves.
• The soil looks dry.
• One leaf is drooping.

What makes this science? These are careful observations about the natural world. The student is noticing facts, not opinions.

Worked Example 2: Testing sunlight and shade

Question: Do plants grow better in sunlight or shade?

Steps:

1. Use 2 similar plants.
2. Give both plants the same amount of water.
3. Put one plant in sunlight and one plant in shade.
4. Measure each plant every few days.

Result: After two weeks, the plant in sunlight is taller.

Conclusion: The evidence shows that the plant in sunlight grew more. Sunlight helped this plant grow better.

Worked Example 3: Looking for a pattern

Question: Does a toy car roll farther on tile or carpet?

Test results:

• Tile: 40 cm, 42 cm, 41 cm
• Carpet: 18 cm, 20 cm, 19 cm

Pattern: The car rolled farther each time on tile than on carpet.

Conclusion: The smoother tile helped the car roll farther.

Worked Example 4: Changing an idea with new evidence

First idea: All heavy objects sink.

New observation: A big heavy boat floats on water.

What happens next? The student changes the first idea. Now the student knows that not all heavy things sink.

Why this matters: In science, new evidence can help us make a better explanation.

Science or not science?

Let’s practice thinking about what fits the nature of science.

• “Which snack tastes best?” Not a science question, because it is based on opinion.
• “Which snack has the most raisins?” A science question, because we can count and compare.
• “This flower is pretty.” Opinion, not scientific evidence.
• “This flower has 8 petals.” Observation and evidence.

How you can be a young scientist

• Ask questions about the world around you.
• Look closely and observe carefully.
• Use tools the right way.
• Write down what you notice.
• Use evidence to answer questions.
• Be honest about your results.
• Listen to new evidence and be willing to learn.

Brief Summary

The nature of science is about how we learn, not just what we know. Scientists ask testable questions, make observations, gather evidence, look for patterns, and explain results. They work safely and honestly, and they may change their ideas when new evidence is found.

Formulating Testable Questions means asking a question that you can investigate by doing an experiment or making careful observations.

Scientists ask many kinds of questions. Some questions are good for talking about or reading about. Other questions are good for testing. In science, a testable question is a question you can answer by trying something out, measuring, counting, or observing what happens.

For example, the question "Why is the sky beautiful?" is not testable because different people may have different ideas. But the question "Does the sky look darker when there are more clouds?" is testable because you can observe the sky and compare what you see.

A good testable question usually asks how one thing changes another thing. It often starts with words like:

• What happens if...?
• How does ... affect ...?
• Which ... works best?
• Does ... change ...?

These question starters help us make questions that are clear and can be tested.

When you make a testable question, think about two important parts:

• What you change — the one thing you try differently
• What you observe or measure — what you watch, count, or measure to see the result

For example, if you want to know about plants, you might change the amount of water. Then you might measure how tall the plant grows.

So a testable question could be: "How does the amount of water affect how tall a plant grows?"

This is testable because:

• You can give plants different amounts of water.
• You can measure each plant's height.
• You can compare the results.

A question is not testable if it:

• asks for an opinion, like "Which flower is the prettiest?"
• is too big or too general, like "Why do plants grow?"
• cannot be observed or measured easily

Let’s look at how to turn a curious question into a testable one.

Curious question: "Which paper towel is the best?"

This is not a good testable question yet because best could mean many things. Does best mean strongest? Most absorbent? Softest?

We can make it testable by being more specific:

• Which paper towel brand soaks up the most water?
• Which paper towel brand holds the most pennies before tearing?

Now the question is clear. We know what to test and what to measure.

Here are some clues that a question may be testable:

• You can do an experiment safely.
• You can use tools like a ruler, cup, timer, or balance.
• You can count, measure, or observe the results.
• You can compare one result to another.

Here are some clues that a question may not be testable:

• It asks what someone likes best.
• It uses unclear words like best, nice, or beautiful without saying what that means.
• It is too broad to test in one simple investigation.

How to build a testable question

1. Pick one thing you will change.
2. Pick one thing you will observe or measure.
3. Write the question clearly.
4. Make sure you can test it safely.

You can use this simple frame:

How does _____ affect _____?

For example:

• How does sunlight affect plant growth?
• How does ramp height affect how far a toy car rolls?
• How does water temperature affect how fast sugar dissolves?

Each question tells what will be changed and what will be measured.

Worked Example 1

Question: "Do bean plants grow better with music?"

This is close to being testable, but the word better is not clear. We need to say what better means.

Make it testable: "Does playing music affect how tall bean plants grow?"

What is changed? Playing music or not playing music.

What is measured? Plant height.

Worked Example 2

Question: "Which fruit is tastiest?"

This is not testable in a science experiment because tastiest is an opinion.

Make it testable: "Which fruit has the most seeds?"

What is changed? The kind of fruit.

What is observed or counted? The number of seeds.

Worked Example 3

Question: "Why do some toys roll faster?"

This question is interesting, but it is too broad for one simple test.

Make it testable: "How does the height of a ramp affect how fast a toy car rolls?"

What is changed? Ramp height.

What is measured? How fast the toy car rolls, maybe by timing it with a stopwatch.

Worked Example 4

Question: "Are big bubbles more fun than small bubbles?"

This is not testable because more fun is an opinion.

Make it testable: "Which bubble wand makes bigger bubbles?"

What is changed? The bubble wand.

What is measured? The size of the bubbles.

Let’s practice spotting the difference.

• Not testable: Which pet is the cutest?
• Testable: Which pet food disappears fastest from a bowl?

• Not testable: Why are rainbows amazing?
• Testable: Does sunlight and water make a rainbow appear?

• Not testable: What is the best way to clean a desk?
• Testable: Which cleaner removes the most marker from a desk?

When scientists ask testable questions, they make sure the question is specific. Specific means clear and exact. A specific question helps you know what to do in the investigation.

For example, instead of asking "What helps plants?" you could ask:

• Does fertilizer affect how tall a plant grows?
• Does the amount of sunlight affect the number of leaves on a plant?

These questions are better because they focus on one thing to change and one thing to measure.

It is also important to change only one thing at a time when possible. If you change too many things, it is hard to know what caused the result.

For example, if one plant gets more water, more sunlight, and a bigger pot, you will not know which change helped it grow. That is why a clear testable question usually focuses on one change.

Scientists also think about safety. A question should be tested in a safe way. Third graders can test many questions with plants, water, paper towels, ramps, magnets, shadows, and other simple materials.

Quick checklist for a testable question

• Is the question clear?
• Can I change one thing?
• Can I observe, measure, or count the result?
• Can I test it safely?

If you can answer yes to all four, your question is probably testable.

Summary

A testable question is a question you can answer by doing an investigation. It should be clear, specific, and safe to test. It usually includes one thing you change and one thing you measure or observe. Questions based on opinions, such as what is prettiest or tastiest, are not testable in science.

Qualitative Observation Techniques are ways scientists describe what they notice using their senses. A qualitative observation tells about a quality, or what something is like, instead of using numbers.

When you make qualitative observations, you use your senses to gather information. In science, we use sight, hearing, touch, and smell. We do not taste things in science unless an adult scientist says it is safe, because tasting can be dangerous.

Qualitative observations help us answer questions like:

• What color is it?
• How does it feel?
• What does it smell like?
• What sound does it make?
• Does it look bigger, smaller, rougher, smoother, darker, or lighter than something else?

These observations are important because they help scientists learn about objects, plants, animals, and materials. Good observations are careful, clear, and based on what you really notice.

What counts as a qualitative observation?

• "The leaf is bright green."
• "The rock feels rough."
• "The flower smells sweet."
• "The bell sounds loud."
• "The puppy's fur looks softer than the towel."

What does not count as a qualitative observation?

• "The stick is 10 centimeters long." That uses a number.
• "The water is 20 degrees." That uses a number.
• "I think the cloud is sad." That is a feeling, not an observation.

Qualitative observations use describing words. These words help paint a picture in someone else's mind.

Words scientists may use

• Color: red, yellow, green, brown, clear, dark, light
• Texture: rough, smooth, bumpy, soft, hard, fuzzy, slippery
• Odor: sweet, strong, stinky, fresh
• Sound: quiet, loud, high, low, buzzing, rustling
• Relative size: bigger, smaller, longer, shorter, wider, narrower
• Shape: round, flat, curved, pointy

How to make a good qualitative observation

1. Look carefully. Notice color, shape, and size.
2. Listen if it makes a sound. Is it quiet or loud?
3. Touch carefully if it is safe. Does it feel smooth, rough, soft, or hard?
4. Smell only if an adult says it is safe. Does it have a strong smell, a sweet smell, or no smell?
5. Use clear describing words. Say exactly what you notice.
6. Write or say only what you observe. Do not guess.

Safety reminder: Never taste items in science class. Also, do not touch or smell something unless your teacher says it is safe.

Observation or opinion?

It is important to know the difference between an observation and an opinion.

• Observation: "The apple is red and smooth."
• Opinion: "The apple looks delicious."

An observation is something you can notice with your senses. An opinion tells what you think or feel.

Observation or guess?

• Observation: "The jar has a strong sour smell."
• Guess: "I think the jar has pickle juice in it."

Scientists try to first record what they notice. They can make guesses later.

Worked Example 1: Observing a leaf

You are given a leaf to study. What qualitative observations can you make?

Step-by-step:

• Look at it: The leaf is green.
• Look at the edges: The edges are pointy.
• Touch it carefully: It feels smooth on top and a little bumpy underneath.
• Smell it if safe: It has a fresh smell.

Good qualitative observations: "The leaf is green, pointy, smooth on top, bumpy underneath, and has a fresh smell."

Worked Example 2: Observing two rocks

You have two rocks. One is dark and rough. The other is light and smooth. How can you compare them using qualitative observations?

Step-by-step:

• Look at both rocks.
• Notice color differences.
• Touch both rocks carefully.
• Use comparison words.

Good qualitative comparison: "Rock A is darker and rougher than Rock B. Rock B is lighter and smoother than Rock A."

This is qualitative because it uses describing words, not numbers.

Worked Example 3: Observing a cup of water and a cup of juice

You see one cup with water and one cup with orange juice. What can you observe without tasting?

Step-by-step:

• Look: The water is clear. The juice is orange.
• Smell if safe: The water has little or no smell. The juice smells fruity.
• Compare: The juice is darker than the water.

Good qualitative observations: "The water is clear and has little or no smell. The juice is orange, smells fruity, and looks darker than the water."

Worked Example 4: Is it qualitative?

Read each sentence and decide if it is a qualitative observation.

• "The teddy bear feels soft." Yes, because it describes texture.
• "The teddy bear weighs 2 pounds." No, because it uses a number.
• "The drum sounds loud." Yes, because it describes sound.
• "I like the drum." No, because that is an opinion.

Tips for strong science observations

• Be calm and careful.
• Take your time and notice small details.
• Use your senses safely.
• Choose exact words.
• Record what you observe, not what you imagine.

Let’s practice with everyday objects

If you observe a pencil, you might say:

• "The pencil is yellow."
• "It feels smooth."
• "It has a pointy tip."
• "The eraser is soft."

If you observe a sponge, you might say:

• "The sponge is squishy."
• "It feels rough on one side and soft on the other side."
• "It is bigger than the eraser."

Why qualitative observations matter

Scientists use qualitative observations to describe the world clearly. These details help them compare objects, notice changes, and share what they learn with others.

For example, if a plant changes from green to brown, or if a puddle has no smell one day but a strong smell later, those observations can help scientists understand what is happening.

Summary

Qualitative observation techniques help us describe things using our senses. We use sight, hearing, touch, and smell, but not taste. Good qualitative observations use clear describing words like color, texture, odor, sound, shape, and relative size. Scientists record what they really notice so they can learn more about the world.

Quantitative Observation and Measurement

Scientists learn about the world by observing. An observation is something you notice with your senses or with tools.

Sometimes scientists use words to describe what they see. For example, “The rock is rough” or “The water feels cold.” These are good observations, but they do not use numbers.

Other times, scientists use numbers and units. For example, “The rock is 8 centimeters long” or “The water temperature is 10 degrees.” These observations are called quantitative observations.

Quantitative means “using numbers.” A quantitative observation tells how much, how many, how long, or how heavy.

Measurement is how we find these numbers. We use tools and standard units so other people can understand our results.

Why do scientists measure?

• To be exact and clear
• To compare objects fairly
• To record data that others can use
• To notice changes over time

When everyone uses the same units, measurements make more sense. If one student says a plant is 12 centimeters tall, another student can understand exactly how tall it is.

Common things scientists measure

• Length or height: how long or tall something is
• Mass: how much matter is in something
• Volume: how much space a liquid takes up
• Time: how long something lasts

1. Measuring length and height

Length tells how long something is. Height tells how tall something is. We often measure these with a ruler or a meter stick.

Common units for length are centimeters (cm) and meters (m).

• Use centimeters for small objects, like a leaf or pencil.
• Use meters for bigger things, like a desk or a room.

To measure correctly:

1. Put the object at the 0 mark on the ruler.
2. Keep the ruler straight.
3. Look at where the object ends.
4. Write the number and the unit.

Example: A crayon is 9 centimeters long. We write 9 cm.

2. Measuring mass

Mass tells how much matter is in an object. A balance or scale can help measure mass.

A common unit for mass is grams (g).

• Use grams for light objects, like an eraser or an apple.

Example: An apple might have a mass of 120 g.

3. Measuring volume

Volume tells how much space a liquid takes up. We often measure liquid volume with a measuring cup or a graduated container.

A common unit for liquid volume is milliliters (mL).

• Use milliliters for liquids like water, juice, or oil.

Example: A cup may hold 200 mL of water.

4. Measuring time

Time tells how long something takes. We measure time with a clock, stopwatch, or timer.

Common units for time are seconds, minutes, and hours.

• Use seconds for short events, like a toy car rolling down a ramp.
• Use minutes for medium-length events, like reading.
• Use hours for longer events, like a trip or a school day.

Example: A student may run across the playground in 15 seconds.

Standard units are important

A standard unit is a unit that many people use in the same way. Standard units help measurements stay fair and clear.

Imagine one student measures a desk with hand spans and another uses paper clips. Their answers may be very different. But if both students use centimeters, they can compare their results better.

Be objective

Quantitative observations are objective. That means they are based on facts and numbers, not opinions.

Compare these two observations:

• “The worm is tiny.”
• “The worm is 6 cm long.”

The second observation is more exact because it uses a number and a unit.

Worked Example 1: Measuring length

Lena measures a leaf with a ruler. The leaf starts at 0 and ends at 7 on the centimeter side.

Question: How long is the leaf?

Think: We read the ruler from 0 to where the leaf ends.

Answer: The leaf is 7 cm long.

This is a quantitative observation because it uses a number and a unit.

Worked Example 2: Measuring volume

Jay pours water into a measuring cup. The water line stops at 150 milliliters.

Question: What is the volume of the water?

Answer: The water has a volume of 150 mL.

Now Jay can compare this amount of water with other amounts in the same unit.

Worked Example 3: Measuring time

A toy spinner spins for 12 seconds before it stops.

Question: What quantitative observation can we write?

Answer: The toy spinner spun for 12 seconds.

This is better than saying, “The spinner spun for a long time,” because “12 seconds” is exact.

Worked Example 4: Comparing measurements

Two pencils are measured.

• Pencil A: 10 cm
• Pencil B: 14 cm

Question 1: Which pencil is longer?

Think: Compare the numbers. Since \(14 > 10\), Pencil B is longer.

Answer 1: Pencil B is longer.

Question 2: How much longer is Pencil B?

Think: Subtract the smaller length from the bigger length.

$$14 - 10 = 4$$

Answer 2: Pencil B is 4 cm longer.

Tips for careful measuring

• Choose the correct tool for the job.
• Choose the correct unit.
• Start at 0 on the measuring tool.
• Keep the tool straight and still.
• Read the measurement carefully.
• Always write the number and the unit.

Examples of tools and what they measure

• Ruler or meter stick → length or height
• Scale or balance → mass
• Measuring cup → volume
• Clock or stopwatch → time

Quantitative or not?

Let’s look at some observations.

• “The flower is pretty.” → Not quantitative
• “The flower is 12 cm tall.” → Quantitative
• “The soup is hot.” → Not quantitative
• “The timer says 3 minutes.” → Quantitative

If the observation uses a number and usually a unit, it is quantitative.

How scientists record data

Scientists often write measurements in a chart or notebook. This helps them remember what they found and compare results later.

For example:

• Plant height on Monday: 9 cm
• Plant height on Friday: 11 cm

These measurements show that the plant grew.

We can find how much it grew:

$$11 - 9 = 2$$

The plant grew 2 cm.

Summary

Quantitative observations use numbers and units. They help scientists describe things clearly and fairly.

Scientists measure length, mass, volume, and time using tools such as rulers, scales, measuring cups, and clocks.

When you measure carefully and use standard units like cm, g, mL, and seconds, your observations become more useful and more scientific.

Experimental Design Fundamentals means learning how to do a fair test.

When scientists want to learn something, they do not change everything at once. They change one thing, watch what happens, and keep the other things the same.

In 1st grade, we can think about it like this:

• Change one thing
• Watch what happens
• Keep the rest the same

This helps us know why something happened.

For example, if one plant gets more water and more sunlight, we will not know if the water helped or the sunlight helped. That is not a fair test.

A fair test helps us answer a question clearly.

Step 1: Ask a testable question.

A testable question is a question we can try out and observe.

• "Does a plant grow taller with more water?"
• "Which toy car rolls farther?"
• "Does ice melt faster in the sun or in the shade?"

These are good science questions because we can test them.

Step 2: Choose the one thing to change.

This is the thing we change on purpose.

For young scientists, we can call it the one thing we change.

Examples:

• how much water a plant gets
• which ramp a toy car uses
• whether ice is in the sun or shade

Step 3: Choose the thing to measure or observe.

This is what we watch to see what happens.

For young scientists, we can call it the thing we measure.

Examples:

• how tall the plant grows
• how far the toy car rolls
• how fast the ice melts

Step 4: Keep the other things the same.

This is what makes the test fair.

If we are testing water for plants, we should keep these the same:

• same kind of plant
• same size pot
• same soil
• same place by the window

Only the water should change.

Why do we keep things the same?

We keep things the same so we can tell what caused the change.

If too many things change, the test is confusing.

Think of it this way:

• One thing changes.
• One result is measured.
• Everything else stays the same.

Scientists also collect data.

Data means the information we gather.

We can collect data by:

• counting
• measuring
• looking carefully
• drawing what we see

Sometimes we use numbers. For example, if one car rolls 5 blocks and another rolls 8 blocks, we can compare them.

We can write that as \(5\) and \(8\).

Since \(8 > 5\), the second car rolled farther.

Worked Example 1: Which paper towel soaks up more water?

Question: Which paper towel picks up more water?

One thing to change: the kind of paper towel

Thing to measure: how much water each towel soaks up

Keep the same:

• same amount of water to start
• same size towel pieces
• same time in the water

Why this is fair: Only the towel kind changes.

Worked Example 2: Do bigger toy cars roll farther?

Question: Does a bigger toy car roll farther?

One thing to change: the size of the toy car

Thing to measure: how far the car rolls

Keep the same:

• same ramp
• same starting place
• same floor
• same push, or no push at all

If one car starts higher up and another starts lower down, the test is not fair.

Worked Example 3: Does more water help a plant grow taller?

Question: Does more water help a plant grow taller?

One thing to change: how much water each plant gets

Thing to measure: plant height

Keep the same:

• same kind of plant
• same pot
• same soil
• same sunlight

Imagine Plant A gets 1 cup of water and Plant B gets 2 cups of water.

After some days, we measure:

• Plant A = \(6\) inches
• Plant B = \(8\) inches

We can compare the heights:

$$8 > 6$$

Plant B is taller.

Because the other things stayed the same, we can say the amount of water may have helped make the difference.

Worked Example 4: Does ice melt faster in the sun?

Question: Does ice melt faster in the sun or in the shade?

One thing to change: where the ice is placed

Thing to measure: how long it takes to melt

Keep the same:

• same size ice cubes
• same kind of plate
• same starting time

If the ice cube in the sun is small and the one in the shade is big, the test is not fair.

How to plan a fair test

1. Ask a science question.
2. Pick one thing to change.
3. Pick one thing to measure.
4. Keep the other things the same.
5. Observe carefully.
6. Write or draw what happened.

Let’s practice thinking.

You want to know if seeds grow better in sunlight or darkness.

• One thing to change: light or dark
• Thing to measure: how much the seed grows
• Keep the same: same seed type, same water, same cup, same soil

That is a fair test.

Now imagine one seed gets more water too. Then the test is not fair, because two things changed.

Clues that a test is fair:

• Only one thing is different.
• You know what you are measuring.
• The rest stays the same.

Clues that a test is not fair:

• Many things change at once.
• You do not know what to measure.
• The objects are not treated the same.

Important idea: A fair test helps us use evidence.

Evidence is what we saw, counted, or measured.

Instead of saying, "I just think so," we can say, "I measured it," or "I observed it."

Summary

Experimental design fundamentals are about planning a fair test.

We change one thing, measure what happens, and keep the other things the same.

When we do this, we can learn from our observations and make a smart science answer.

Identifying and Using Scientific Tools

Scientists use tools to help them learn about the world. Some things are too small to see well, too tiny to weigh in our hands, or need careful measuring. Scientific tools help us observe, measure, and compare.

In 3rd Grade, you will learn how to identify common scientific tools and use them safely. When we choose the right tool, we can do a better job answering science questions.

What does a scientific tool do?

A scientific tool helps us gather information. It can help us:

• See things better
• Measure how much, how heavy, or how hot something is
• Compare objects
• Record what we notice

Let’s learn about some common science tools.

1. Hand Lens

A hand lens is a magnifying tool. It makes small objects look bigger. Scientists use it to look closely at things like leaves, rocks, insects, and cloth.

When to use it: Use a hand lens when you need to see details that are hard to see with just your eyes.

How to use it safely:

• Hold the hand lens close to your eye or close to the object.
• Move it slowly until the object looks clear.
• Do not use it to look at the Sun. That can hurt your eyes.

2. Microscope

A microscope helps us see very tiny things much bigger. It can show details that a hand lens cannot. Scientists use microscopes to look at very small objects.

When to use it: Use a microscope when an object is too tiny to see clearly with your eyes or a hand lens.

How to use it safely:

• Carry it carefully with two hands if your teacher says it is okay to move it.
• Put it on a flat table.
• Look through the eyepiece gently.
• Turn knobs slowly.
• Listen to your teacher’s directions.

3. Balance

A balance measures how heavy something is. In science, we often compare the mass of objects using a balance. A balance helps us know which object has more or less mass.

When to use it: Use a balance when you want to compare the mass of two objects or find how much an object weighs on the balance.

How to use it safely:

• Place the balance on a flat surface.
• Set objects gently on the tray or pan.
• Do not push down on the balance.
• Do not place wet or messy objects on it unless your teacher says it is okay.

4. Thermometer

A thermometer measures temperature. Temperature tells us how hot or cold something is.

When to use it: Use a thermometer to measure the temperature of air, water, or another material.

How to use it safely:

• Handle it carefully.
• Do not swing it around.
• Read the numbers at eye level.
• Use it only the way your teacher shows you.

If one cup of water is 10 degrees cooler than another, we can show that with math:

$$30 - 20 = 10$$

This means one sample is 10 degrees cooler.

5. Graduated Cylinder

A graduated cylinder measures how much liquid there is. It measures volume. Volume means how much space a liquid takes up.

When to use it: Use a graduated cylinder when you want to measure water, juice, or another liquid in science class.

How to use it safely:

• Set it on a flat table.
• Pour slowly.
• Look at the measurement line at eye level.
• Be careful not to spill.

Choosing the Right Tool

A big part of science is picking the best tool for the job. Ask yourself:

• Do I need to look closely?
• Do I need to measure how hot or cold something is?
• Do I need to measure how much liquid there is?
• Do I need to compare how heavy objects are?

Here is a simple guide:

• Hand lens → to see small details
• Microscope → to see very tiny things
• Balance → to measure or compare mass
• Thermometer → to measure temperature
• Graduated cylinder → to measure liquid volume

Why safety matters

Scientists work carefully. Using tools the right way keeps people safe and helps us get good results.

Here are important safety rules:

• Follow directions from your teacher.
• Use tools only for their science job.
• Carry tools carefully.
• Keep your work area neat.
• Tell an adult if something spills or breaks.
• Never taste science materials unless your teacher says it is safe.

Worked Example 1: Looking at a Leaf

Question: Maya wants to see the tiny lines on a leaf. What tool should she use?

Think: She needs to look closely at small details.

Answer: She should use a hand lens.

Why: A hand lens makes small details look bigger and easier to see.

Worked Example 2: Measuring Water

Question: Ben wants to know how much water is in a container. What tool should he use?

Think: He is measuring a liquid.

Answer: He should use a graduated cylinder.

Why: A graduated cylinder measures liquid volume.

If Ben pours water up to the 40 mark, then the amount is 40 units of liquid. If he adds 10 more units, we can write:

$$40 + 10 = 50$$

Now the graduated cylinder shows 50 units of liquid.

Worked Example 3: Comparing Two Rocks

Question: Sara has two rocks. She wants to know which one has more mass. What tool should she use?

Think: She wants to compare how heavy the rocks are.

Answer: She should use a balance.

Why: A balance helps compare the mass of objects.

If one rock has a mass of 8 units and the other has a mass of 5 units, then the difference is:

$$8 - 5 = 3$$

The first rock has 3 more mass units than the second rock.

Worked Example 4: Hot and Cold Water

Question: A student wants to know which cup of water is warmer. One cup is 18 degrees and one cup is 25 degrees. What tool should the student use, and which cup is warmer?

Think: The student needs to measure temperature.

Answer: The student should use a thermometer. The 25-degree cup is warmer.

Why: A thermometer measures temperature, and 25 is greater than 18.

We can show the difference like this:

$$25 - 18 = 7$$

The warmer cup is 7 degrees warmer.

Tips for Success

• First, think about what you want to learn.
• Next, choose the tool that matches the job.
• Then, use the tool carefully and correctly.
• Finally, record what you observe or measure.

Quick Review

• A hand lens helps you see small details.
• A microscope helps you see very tiny things.
• A balance helps you measure or compare mass.
• A thermometer helps you measure temperature.
• A graduated cylinder helps you measure liquids.

Summary

Scientific tools help us learn more about objects and materials. Each tool has a special job. When you choose the correct tool and use it safely, you can make careful observations and measurements like a scientist.

Measurement: Length and Distance helps us describe how long something is or how far apart things are. Scientists measure carefully so they can compare objects, record information, and share what they learn with others.

When we measure length, we are finding how long, tall, or wide something is. When we measure distance, we are finding how far it is from one place to another.

To measure well, scientists use tools and standard units. Standard units are agreed-upon sizes that everyone can use. This helps people get the same kind of answer.

Some common tools for measuring length and distance are:

• Ruler for small objects
• Yardstick or meter stick for longer objects
• Measuring tape for curved or longer distances

There are two common systems of measurement:

• Imperial units: inches, feet, yards
• Metric units: centimeters, meters

Here are some standard units you may use:

• Inch (in.) — good for small objects
• Foot (ft) — longer than an inch
• Yard (yd) — longer than a foot
• Centimeter (cm) — good for small objects
• Meter (m) — longer than a centimeter

These units are related to each other:

$$12 \text{ inches} = 1 \text{ foot}$$

$$3 \text{ feet} = 1 \text{ yard}$$

$$100 \text{ centimeters} = 1 \text{ meter}$$

In 3rd Grade, it is most important to know which unit makes sense. For example, a pencil is better measured in inches or centimeters, but a classroom is better measured in feet or meters.

One very important rule when using a ruler is to start at the zero point. The zero point is where the measuring begins. On most rulers, this is the line marked 0.

If you start measuring at the edge of the ruler instead of the zero mark, your answer might be wrong. Sometimes the ruler’s edge is damaged or does not line up exactly with zero. Scientists check the zero point first so their measurements are accurate.

To measure an object correctly:

1. Put one end of the object at the 0 mark.
2. Keep the ruler straight along the object.
3. Look at where the other end stops.
4. Read the number and unit.

If an object does not start at zero, you can still find its length. Measure both ends and subtract.

For example, if one end is at \(2\) cm and the other end is at \(9\) cm, then:

$$9 - 2 = 7$$

So the object is 7 cm long.

Choosing the right unit is part of good science. Here are some smart choices:

• A leaf: centimeters or inches
• A book: centimeters or inches
• A desk: feet or meters
• The length of the playground: yards or meters

Scientists also compare measurements. They may ask:

• Which object is longer?
• Which distance is shorter?
• How much longer is one object than another?

To find how much longer one object is, subtract the smaller length from the larger length.

For example, if one ribbon is \(10\) inches long and another ribbon is \(6\) inches long:

$$10 - 6 = 4$$

The first ribbon is 4 inches longer.

Worked Example 1: Measuring from zero

A crayon starts at the \(0\) mark on a ruler and ends at \(5\) inches. How long is the crayon?

Step 1: Check that the crayon starts at \(0\).

Step 2: Read where the other end stops: \(5\).

Answer: The crayon is 5 inches long.

Worked Example 2: Measuring when the object does not start at zero

A shell lies on a ruler. One end is at \(3\) cm and the other end is at \(8\) cm. How long is the shell?

Step 1: Find the end numbers: \(3\) cm and \(8\) cm.

Step 2: Subtract:

$$8 - 3 = 5$$

Answer: The shell is 5 cm long.

Worked Example 3: Choosing the best unit

What is the best unit to measure the length of a classroom: centimeters, inches, or feet?

Think: A classroom is large, so small units like centimeters and inches are not the best choice.

Answer: Feet is a good choice. Meters would also make sense.

Worked Example 4: Comparing two lengths

A stick is \(9\) centimeters long. A pencil is \(6\) centimeters long. How much longer is the stick?

Step 1: Compare the numbers: \(9\) and \(6\).

Step 2: Subtract:

$$9 - 6 = 3$$

Answer: The stick is 3 centimeters longer than the pencil.

Tips for careful measuring:

• Always check the zero point.
• Keep the ruler straight.
• Use the correct unit.
• Read the ruler carefully.
• Write the number and the unit, such as \(7\) cm or \(4\) in.

Why measurement matters in science:

Scientists measure plants, rocks, animal tracks, and many other things. Careful measurement helps them notice patterns, compare results, and explain what they found.

If two students measure the same object correctly with the same unit, their answers should be very close or the same. That is why using standard units and starting at zero are so important.

Summary

Length tells how long something is, and distance tells how far apart things are. We use tools like rulers, meter sticks, yardsticks, and measuring tape to measure. Good measuring means using standard units such as inches, feet, centimeters, and meters, choosing a unit that fits the object, and always checking the ruler’s zero point. When an object does not start at zero, subtract the smaller number from the larger number to find its length.

Scientific Tool Selection and Usage

Scientists use tools to help them learn about the world. Tools help us see, measure, compare, and observe things better.

Sometimes our eyes, hands, and ears are enough. But sometimes we need a tool to help. A hand lens can help us see tiny details. A balance can help us compare weight. A thermometer can help us find out if something is warmer or cooler.

Learning to pick the right tool is an important science skill. Learning to use the tool the right way is important too.

What is a scientific tool?

A scientific tool is something we use to help us observe or measure. Tools help us get better information.

• Hand lens: helps us look closely at small things.
• Microscope: helps us see very tiny things much bigger.
• Balance: helps us compare which object is heavier or lighter.
• Thermometer: helps us measure how hot or cold something is.
• Ruler: helps us measure how long something is.

Why do scientists use tools?

Scientists use tools to extend their senses. That means tools help them do more than eyes, ears, nose, hands, and mouth can do alone.

• Our eyes can see a leaf, but a hand lens helps us see its tiny lines.
• Our hands can feel that one rock is heavier, but a balance helps us compare carefully.
• Our skin can feel warm or cool, but a thermometer gives a number.

Numbers and careful observations help scientists learn and share what they find.

How to choose the right tool

When we choose a tool, we ask, “What am I trying to learn?”

• If you want to see tiny details, use a hand lens or microscope.
• If you want to know which object is heavier, use a balance.
• If you want to know how warm or cold something is, use a thermometer.
• If you want to know how long something is, use a ruler.

Using the wrong tool will not help very much. A thermometer cannot show tiny bug wings. A hand lens cannot tell the temperature.

Using a hand lens

A hand lens helps us make small things look bigger. It is good for looking at leaves, sand, cloth, insects, and rocks.

1. Hold the hand lens near your eye.
2. Move the object closer or farther until it looks clear.
3. Look for details like lines, spots, colors, or shapes.

Be gentle. Do not press the hand lens onto the object. Hold it carefully.

Using a microscope

A microscope helps us see things that are very tiny. In 1st grade, you may use a simple classroom microscope with help from a teacher.

1. Place the object where it belongs.
2. Look through the lens.
3. Turn or move the part that makes the picture clear.
4. Observe what you see.

Microscopes should be used gently and carefully. Ask for help if you need it.

Using a balance

A balance helps us compare weight. It can show which object is heavier, which is lighter, or if they are the same.

1. Make sure the balance is empty and even before you start.
2. Put one object on one side.
3. Put the other object on the other side.
4. Watch what happens.

• If one side goes down, that side is heavier.
• If one side stays up, that side is lighter.
• If both sides stay even, the objects are the same weight.

Before using a balance, we check that it starts in the middle or level. This is a way to make sure the tool is ready to use correctly.

Using a thermometer

A thermometer tells us temperature. Temperature means how hot or cold something is.

1. Look at the thermometer before you begin.
2. Make sure it is ready to read.
3. Place it where you are measuring, if your teacher says it is safe.
4. Wait a little.
5. Read the number.

We do not guess temperature by touch alone. Something may feel cool or warm, but a thermometer helps us measure it more carefully.

What does “ready to use” mean?

Scientists make sure tools are ready before using them. This helps them get good information.

For young scientists, this can mean:

• The hand lens is clean.
• The microscope picture is made clear.
• The balance starts level.
• The thermometer is easy to read.

This is part of using tools the right way.

Be safe and careful with tools

• Carry tools gently.
• Use tools only the way your teacher shows you.
• Keep tools clean.
• Put tools back where they belong.
• Ask for help with breakable tools.

Worked Example 1: Looking at a leaf

Question: Maya wants to see the tiny lines on a leaf. Which tool should she use?

Think: She wants to see small details.

Best tool: A hand lens.

Why? A hand lens makes the small parts of the leaf look bigger, so Maya can see the lines more clearly.

Worked Example 2: Which rock is heavier?

Question: Ben has two rocks. He wants to know which rock is heavier. Which tool should he use?

Think: He wants to compare weight.

Best tool: A balance.

How to use it:

1. Check that the balance starts level.
2. Put one rock on each side.
3. See which side goes down.

Answer: The side that goes down has the heavier rock.

Worked Example 3: Is the water warm or cold?

Question: Ana wants to know the temperature of water. Which tool should she use?

Think: She wants to measure how warm or cold it is.

Best tool: A thermometer.

Why not use a hand lens? A hand lens helps us see better, but it does not measure temperature.

Answer: Ana should use a thermometer and read the number.

Worked Example 4: Tiny things on a feather

Question: Leo wants to look at very tiny parts of a feather that are hard to see. Should he use a ruler, a microscope, or a balance?

Think: He wants to see something very tiny.

Best tool: A microscope.

Why? A microscope helps very tiny things look much bigger.

Not the other tools:

• A ruler measures length.
• A balance compares weight.

Let’s remember

• Choose the tool that matches the job.
• Use the tool carefully and the right way.
• Make sure the tool is ready before you start.
• Tools help scientists observe and measure better.

Quick tool guide

• See small details: hand lens
• See very tiny things: microscope
• Compare heavier or lighter: balance
• Measure hot or cold: thermometer
• Measure length: ruler

Summary

Scientific tools help us learn more about the world. A hand lens and microscope help us see better, a balance helps us compare weight, and a thermometer helps us measure temperature.

Good scientists pick the right tool for the job, make sure it is ready, and use it carefully. When we use tools the right way, we get better observations and better answers.

Measurement: Volume and Capacity helps us describe how much space something takes up.

In science, we measure many things. We might measure length, mass, temperature, and also volume and capacity. These measurements help us observe carefully and compare objects in a fair way.

Volume is the amount of space an object or a liquid takes up.

Capacity is how much a container can hold.

These ideas are connected. For example, a bottle has a capacity of how much juice it can hold. The juice inside also has a volume.

Scientists use tools with marks on the side to measure liquids. These tools can include measuring cups, beakers, and graduated cylinders. The marks show how much liquid is in the container.

We often measure liquid volume and capacity in milliliters and liters.

• milliliter (mL): a small amount of liquid
• liter (L): a larger amount of liquid

For example, a medicine cup might hold a few milliliters, but a large bottle of water might hold 1 liter.

Here is one helpful fact:

$$1 \text{ L} = 1000 \text{ mL}$$

That means 1 liter is the same as 1000 milliliters.

When measuring a liquid, it is important to:

1. Put the container on a flat surface.
2. Look at the measurement marks carefully.
3. Keep your eyes level with the top of the liquid.
4. Read the number at the liquid line.

This helps scientists make careful and accurate measurements.

Let’s think about the difference between volume and capacity in a simple way.

• The capacity of a fish tank is how much water it can hold when full.
• The volume of water inside the fish tank is how much water is actually in it right now.

An object that is not a liquid also takes up space. A rock, a toy, or a marble all have volume because they fill part of the space around them.

Sometimes scientists find the volume of a solid object by using water displacement.

Water displacement means placing an object in water and seeing how much the water level rises. The amount the water rises tells the volume of the object.

This works best for solid objects that can go in water without being harmed.

Here are the steps for water displacement:

1. Pour water into a marked container.
2. Read and record the starting water level.
3. Carefully place the object into the water.
4. Read and record the new water level.
5. Subtract to find how much the water rose.

The change in water level is the object’s volume.

We can write that idea like this:

$$\text{Object volume} = \text{new water level} - \text{starting water level}$$

Worked Example 1: Reading a marked container

A measuring cup shows the juice level at \(300\text{ mL}\). How much juice is in the cup?

Step 1: Read the mark where the liquid reaches.

Step 2: The liquid reaches \(300\text{ mL}\).

Answer: There are \(300\text{ mL}\) of juice in the cup.

Worked Example 2: Thinking about capacity

A bottle can hold \(1\text{ L}\) of water. Right now, it has \(600\text{ mL}\) in it. Is the bottle full?

Step 1: Change 1 liter to milliliters.

$$1\text{ L} = 1000\text{ mL}$$

Step 2: Compare \(600\text{ mL}\) to \(1000\text{ mL}\).

Since \(600\text{ mL}\) is less than \(1000\text{ mL}\), the bottle is not full.

Answer: No, the bottle is not full.

Worked Example 3: Finding how much more a container can hold

A pitcher has a capacity of \(2\text{ L}\). There is \(1\text{ L}\) of water inside. How much more water can it hold?

Step 1: Think about the total capacity.

The pitcher can hold \(2\text{ L}\).

Step 2: Subtract the amount already inside.

$$2\text{ L} - 1\text{ L} = 1\text{ L}$$

Answer: The pitcher can hold \(1\text{ L}\) more water.

Worked Example 4: Using water displacement

A scientist puts water in a marked container. The starting level is \(200\text{ mL}\). Then the scientist places a small rock in the water. The new water level is \(260\text{ mL}\). What is the volume of the rock?

Step 1: Write the starting and new water levels.

• Starting level: \(200\text{ mL}\)
• New level: \(260\text{ mL}\)

Step 2: Subtract.

$$260\text{ mL} - 200\text{ mL} = 60\text{ mL}$$

Answer: The rock has a volume of \(60\text{ mL}\).

Let’s look at some ways volume and capacity are used in real life.

• Measuring water for a plant
• Checking how much soup fits in a bowl
• Finding how much liquid is in a bottle
• Testing the volume of a small rock or toy with water displacement

Scientists must also work safely when measuring.

• Use containers carefully so they do not spill.
• Do not put electrical items near water.
• Handle glass containers gently.
• Ask an adult before measuring unknown liquids.

Here are some important ideas to remember:

• Volume is the amount of space something takes up.
• Capacity is how much a container can hold.
• Liquids are often measured in milliliters and liters.
• $$1 \text{ L} = 1000 \text{ mL}$$
• Water displacement helps us find the volume of some solid objects.

When scientists measure carefully, they can collect good data. Good data helps them answer questions and learn more about the world.

Quick Review

1. If a cup holds \(250\text{ mL}\), that is its capacity.
2. If there are \(150\text{ mL}\) of milk in the cup, that is the milk’s volume.
3. If a toy makes the water rise from \(100\text{ mL}\) to \(140\text{ mL}\), the toy’s volume is \(40\text{ mL}\).

Summary

Volume tells how much space an object or liquid takes up. Capacity tells how much a container can hold. We measure liquids with marked tools using liters and milliliters, and we can find the volume of some solid objects by using water displacement.

Measurement: Temperature and Thermal Change

Have you ever touched an ice cube and then held a warm mug? They feel very different. Scientists use temperature to measure how hot or cold something is.

Temperature helps us describe the world around us. We can measure the air outside, a cup of water, or our own body temperature. When temperature goes up or down, we call that a thermal change, which means a change in how warm or cool something is.

In this lesson, you will learn how to read a thermometer, how to use degrees Celsius and degrees Fahrenheit, and how to notice temperature changes over time.

What Is Temperature?

Temperature is a measurement of how hot or cold something is. We measure temperature with a tool called a thermometer.

A thermometer has a scale with numbers. The numbers tell us the temperature in degrees. You may see the degree symbol written like this: \(^\circ\).

• Celsius is written as \(^\circ C\).
• Fahrenheit is written as \(^\circ F\).

Both scales measure temperature, but they use different numbers.

Why Do We Measure Temperature?

Scientists measure temperature to learn about changes in the world. For example, they may check:

• if the day is getting warmer or cooler,
• if water is heating up or cooling down,
• if a freezer is cold enough,
• or if a person's body temperature is normal.

When scientists measure temperature at different times, they can compare the numbers and describe what changed.

What Is a Thermometer?

A thermometer is a tool used to measure temperature. Some thermometers have red or blue liquid inside. Some are digital and show numbers on a screen.

On a thermometer with a scale, the liquid rises when it gets warmer and falls when it gets cooler. To read it, look at the number where the top of the liquid stops.

How to Read a Thermometer

1. Look at the scale and find the numbers.
2. Notice whether the thermometer is in \(^\circ C\) or \(^\circ F\).
3. Find the top of the liquid or the number on the digital screen.
4. Read the temperature carefully.

If the top of the liquid is between two numbers, use the marks between them to help you read the temperature.

Celsius and Fahrenheit

Celsius and Fahrenheit are two ways to measure temperature. A thermometer may show one scale or both scales.

• In Celsius, water freezes at \(0^\circ C\).
• In Celsius, water boils at \(100^\circ C\).
• In Fahrenheit, water freezes at \(32^\circ F\).
• In Fahrenheit, water boils at \(212^\circ F\).

You do not need to change one scale into the other to read a thermometer. You just need to know which scale you are using.

Understanding Thermal Change

A thermal change happens when temperature changes. If the number gets bigger, the object or air is getting warmer. If the number gets smaller, it is getting cooler.

We can show this with simple subtraction:

$$\text{change in temperature} = \text{new temperature} - \text{starting temperature}$$

If the answer is positive, the temperature went up. If the answer is negative, the temperature went down.

Worked Example 1: Reading a Simple Temperature

A thermometer shows \(20^\circ C\). What is the temperature?

Step 1: Look at the scale. It is Celsius.

Step 2: Read the number at the top of the liquid.

Answer: The temperature is \(20^\circ C\).

This tells us the object or air is 20 degrees Celsius.

Worked Example 2: Finding If It Got Warmer or Cooler

In the morning, the air was \(60^\circ F\). In the afternoon, it was \(68^\circ F\). Did it get warmer or cooler?

Step 1: Compare the two numbers.

\(68\) is greater than \(60\).

Step 2: Decide what that means.

Because the number went up, it got warmer.

Answer: The temperature got warmer.

Worked Example 3: Finding How Much the Temperature Changed

A cup of water started at \(12^\circ C\). Later, it was \(18^\circ C\). How much did the temperature change?

Use subtraction:

$$18 - 12 = 6$$

Answer: The temperature changed by \(6^\circ C\).

Because the number got bigger, the water became warmer.

Worked Example 4: Cooling Down

Soup was \(90^\circ F\) at lunch time. After sitting on the table, it was \(80^\circ F\). How did the temperature change?

Step 1: Compare the temperatures.

\(80\) is less than \(90\).

Step 2: Subtract to find the difference.

$$90 - 80 = 10$$

Answer: The soup got cooler by \(10^\circ F\).

Tips for Reading Thermometers Carefully

• Always check whether the scale is Celsius or Fahrenheit.
• Read the number at the top of the liquid.
• Look closely at the small marks between numbers.
• Compare temperatures using greater and smaller numbers.
• Use subtraction to find how much the temperature changed.

Temperature Changes Over Time

Scientists often measure temperature more than once. They may check every hour, every day, or every week. This helps them see patterns.

For example, if the temperature at noon is \(70^\circ F\), at 2:00 it is \(74^\circ F\), and at 4:00 it is \(72^\circ F\), the temperature first rises and then falls. Tracking temperature over time helps us understand what is happening.

Safety Note

Some things that are very hot or very cold can hurt your skin. Always ask an adult before touching hot water, ice packs, cooking tools, or science tools. Use thermometers safely and gently.

What Good Scientists Do

Good scientists measure carefully, write down what they observe, and compare results. When reading temperature, they make sure to use the correct scale and record the number clearly.

They may write observations like these:

• The water was \(10^\circ C\) at the start.
• After 5 minutes, it was \(14^\circ C\).
• The temperature increased by \(4^\circ C\).

These notes help scientists explain what happened.

Summary

Temperature tells us how hot or cold something is. We use a thermometer to measure temperature in degrees Celsius or degrees Fahrenheit. When temperature changes, that is a thermal change. If the number goes up, it gets warmer. If the number goes down, it gets cooler. We can compare temperatures and use subtraction to find how much the temperature changed.

Systematic Data Recording means writing down what you observe in a clear, organized way. Scientists do not try to remember everything in their heads. They record what they see, hear, measure, and notice so they can study it later.

When data is recorded systematically, it is put in order. This helps us find patterns, compare results, and explain what happened. Good data recording also helps other people understand our work.

In science, data is information we collect. Data can be words, numbers, pictures, or drawings. For example, you might record that a plant is green, or you might measure that it is 8 centimeters tall.

There are many ways to record data. Third graders often use:

• Data tables to organize numbers and observations in rows and columns
• Lab notebooks to write notes about what happened
• Labeled diagrams to draw and name parts of something you observed

Why is systematic data recording important?

• It helps us remember what happened
• It keeps information neat and easy to read
• It helps us compare one observation to another
• It makes our science work fair and careful
• It helps us share our findings with others

Imagine you are watching the weather for 5 days. If you scribble random notes on scraps of paper, your information may get lost or mixed up. But if you use one table and record each day in the same way, your data is much easier to understand.

Good data recording has a few important parts.

1. A title that tells what the data is about
2. Labels so you know what each part means
3. Dates or times when needed
4. Clear writing or neat numbers
5. One place to keep all the information

Let’s look more closely at each part.

1. Use a title. A title tells what you are observing. A good title might be “Bean Plant Growth” or “Weather for One Week.” A title helps you know what the page or table is about right away.

2. Label your work. Labels are names for columns, rows, or parts of a drawing. In a table, labels might say “Day,” “Height,” or “Color.” In a diagram, labels might point to “leaf,” “stem,” or “root.”

3. Record data in order. Scientists often record by day, time, or trial number. Keeping things in order helps us see change over time. For example, Day 1 should come before Day 2.

4. Write carefully and neatly. If your numbers or words are messy, you may not understand them later. Neat data is useful data.

5. Record what you really observe. Write what you see, not what you guess. If the water looks cloudy, write “cloudy.” If the plant is 7 centimeters tall, write 7 centimeters. Try not to make up information.

Observations and measurements are both important.

• Observations describe what you notice with your senses, like color, shape, smell, or texture
• Measurements use numbers, like length, time, or temperature

For example, if you observe a plant, you might write:

• Observation: The leaves are bright green.
• Measurement: The plant is 9 centimeters tall.

Both kinds of data help us understand more.

Data tables are one of the best tools for systematic data recording. A data table uses rows and columns to organize information. Each row can show one day, one object, or one trial. Each column can show one type of information.

Here is a simple example of a data table for a plant:

Title: Bean Plant Growth

This table is useful because each day is listed in order, and each kind of data has its own column.

Lab notebooks are another useful tool. A lab notebook is a place to keep science notes together. You can write the date, what you did, what you saw, and any measurements you took.

A lab notebook entry might include:

• The date
• The question you are investigating
• What materials you used
• What you observed
• Your data table or drawing

Keeping everything in one notebook helps you stay organized.

Labeled diagrams are helpful when you want to show what something looks like. A labeled diagram is a drawing with names added to important parts.

If you draw a flower, you might label the petals, stem, and leaves. If you draw a rock, you might label its color, shape, and rough edges. Drawings can show details that are hard to explain with words alone.

Worked Example 1: Recording weather data

A class watches the weather for 3 days. They want to record the sky condition each day.

Instead of writing random notes like “sunny Monday cloudy maybe Tuesday,” they make a table.

Why this works:

• The table has a title idea: weather data
• The columns are labeled
• The days are in order
• The observations are easy to read

Worked Example 2: Recording plant growth

A student measures a plant for 4 days. The heights are 2 cm, 4 cm, 4 cm, and 6 cm.

The student records the measurements in a table:

We can see the plant grew from 2 cm to 6 cm. To find how much it grew, we can subtract:

$$6 - 2 = 4$$

So the plant grew 4 centimeters.

Why this works:

• The measurements are in order by day
• The unit cm is included
• The numbers are easy to compare

Worked Example 3: Using observations and a labeled diagram

A student observes a butterfly in the school garden. The student draws the butterfly and labels:

• Wings
• Antennae
• Body

Then the student writes notes:

• Color: orange and black
• Size: small
• Action: flying from flower to flower

Why this works:

• The diagram shows the parts clearly
• The labels help explain the drawing
• The notes add extra observations

Worked Example 4: Fixing messy data

Here is a messy way to record an investigation:

“plant 5 green maybe taller tuesday day 1 was 3 i think”

This is hard to understand because it is out of order and missing labels.

Here is a better way:

Title: Plant Observations

Now the data is much clearer. We know the height on each day, and we know the plant color.

Tips for recording data well

• Write the date or day
• Add a title
• Use labels
• Keep your writing neat
• Put numbers in the correct places
• Use the same unit each time, like centimeters
• Record information right away so you do not forget
• Tell exactly what you observed

Things to avoid

• Leaving out labels
• Writing data in random places
• Guessing instead of observing
• Mixing up days or times
• Using messy handwriting that is hard to read

When scientists record data carefully, they can look back and answer questions such as:

• Did the plant grow each day?
• Which day was the warmest?
• What color were the leaves?
• Did anything change over time?

This is why organized notes, tables, and diagrams are so important. They help turn observations into useful science information.

Summary

Systematic data recording means writing observations and measurements in a clear, organized way. Scientists use tools like data tables, lab notebooks, and labeled diagrams to keep information neat and easy to understand.

When you add titles, labels, dates, and careful notes, your science work becomes stronger. Good data recording helps you remember what happened, compare results, and share your learning with others.

Data Representation and Graphing

Scientists do more than observe. They also record, organize, and share what they find. One helpful way to share information is by using graphs.

A graph turns numbers and facts into a picture. This makes it easier to notice patterns, compare groups, and answer questions. When scientists collect data, graphs help them understand what the data means.

In this lesson, you will learn how to read and make simple graphs. You will also learn how graphs can show trends, or what happens more, less, or most often.

What is data?

Data is information that we collect. Scientists collect data by observing, measuring, counting, and testing.

Here are some examples of data:

• How many sunny days happened this week
• How many seeds grew in each cup
• The favorite fruit of students in a class
• How many inches of rain fell each day

Sometimes data is first written in a table. A table organizes information into rows and columns so it is neat and easy to read.

Why do we use graphs?

Graphs help us:

• Compare different groups
• See patterns quickly
• Find the most and least
• Share results with other people

For example, if a class writes favorite pets in a table, you can read the table. But if the same information is shown in a bar graph, you can quickly see which pet is the most popular.

Important parts of a graph

Most graphs have some important parts. These parts help us understand the information correctly.

• Title: tells what the graph is about
• Labels: tell what each side or section means
• Numbers: show how many or how much
• Categories: the groups being compared

When you read a graph, always look at the title first. Then look at the labels and numbers. This helps you know what the graph is showing.

Types of graphs

There are different kinds of graphs. In 3rd Grade Science, three useful kinds are bar graphs, line plots, and pie charts.

1. Bar Graph

A bar graph uses bars to show and compare amounts in different groups. The bars can go up and down or side to side.

In a bar graph:

• Each bar stands for one group
• The height or length of the bar shows the amount
• Longer or taller bars mean more
• Shorter bars mean less

Bar graphs are great for comparing things like favorite snacks, kinds of weather, or number of plants in different pots.

2. Line Plot

A line plot shows data along a number line. Marks such as Xs are placed above the numbers to show how many times each value happens.

In a line plot:

• Each X stands for one piece of data
• Numbers are in order from least to greatest
• You can quickly see which number happens most often

Line plots are useful when data has number values, like the number of leaves on plants, inches of rain, or the number of birds seen each day.

3. Pie Chart

A pie chart is a circle divided into parts. Each part shows how much of the whole belongs to one group.

In a pie chart:

• The whole circle means all the data together
• Each slice is one part of the whole
• Bigger slices show bigger parts
• Smaller slices show smaller parts

Pie charts are helpful when you want to show how a whole group is split into parts, such as types of lunch choices or kinds of clouds seen in one week.

From a table to a graph

Scientists often begin with a table. Then they use the table to make a graph.

Here is a simple table:

Birds Seen in the School Garden

• Robins: 4
• Sparrows: 2
• Blue jays: 3

If we turn this into a bar graph, each kind of bird gets one bar. The robin bar would go to 4, the sparrow bar would go to 2, and the blue jay bar would go to 3.

Now the data is easier to compare. We can quickly see that robins were seen the most.

How to make a simple bar graph

1. Write a clear title.
2. Choose the categories to place across the bottom or side.
3. Write the numbers in order.
4. Draw one bar for each category.
5. Make each bar match the correct number.

How to read a graph

1. Read the title.
2. Look at the labels.
3. Check the numbers.
4. Compare the bars, Xs, or slices.
5. Ask questions like: Which is most? Which is least? Are any the same?

Worked Example 1: Reading a bar graph

A class counted the kinds of weather during one week.

• Sunny: 3 days
• Cloudy: 2 days
• Rainy: 1 day

If this data is shown on a bar graph, the sunny bar would be the tallest.

Question: Which weather happened the most?

Answer: Sunny, because 3 is greater than 2 and 1.

We can compare the numbers using:

$$3 > 2 > 1$$

Worked Example 2: Making a bar graph from a table

A scientist observed how many worms were found in different garden spots.

• Under a rock: 5
• In soil: 3
• Near grass: 4

To make a bar graph:

1. Title it Worms Found in Garden Spots.
2. Write the categories: Under a rock, In soil, Near grass.
3. Write number marks from 0 to 5.
4. Draw bars to 5, 3, and 4.

Question: Where were the most worms found?

Answer: Under a rock, because that bar goes to 5.

Worked Example 3: Reading a line plot

A student counted how many flowers were blooming in small garden patches. The numbers were:

2, 3, 3, 4, 2, 3

On a line plot:

• Put one X above 2 for each time 2 appears
• Put one X above 3 for each time 3 appears
• Put one X above 4 for each time 4 appears

Count how many times each number appears:

• 2 appears 2 times
• 3 appears 3 times
• 4 appears 1 time

Question: Which number of flowers happened most often?

Answer: 3 flowers, because it has the most Xs.

We can show the counts as:

$$2 + 3 + 1 = 6$$

That means there are 6 total pieces of data.

Worked Example 4: Understanding a pie chart

A class studied insects they saw on the playground:

• Ants: 4
• Butterflies: 2
• Beetles: 2

Altogether, the class saw:

$$4 + 2 + 2 = 8$$

In a pie chart:

• The whole circle stands for 8 insects
• The ants slice is the biggest because 4 is the largest number
• The butterfly and beetle slices are the same size because both are 2

Question: Which insect takes up the largest part of the pie chart?

Answer: Ants.

How graphs help scientists notice trends

A trend is something you notice happening in the data. It helps answer questions about what is changing or what appears most often.

For example:

• If one bar is much taller, that group happened most often.
• If many Xs are above one number, that value is common.
• If one pie slice is largest, that group is the biggest part of the whole.

Scientists use trends to help explain what they observed. A graph does not just show numbers. It helps tell the story of the data.

Tips for success

• Always read the title first.
• Check what the labels mean.
• Count carefully.
• Make sure bars match the correct numbers.
• Look for the greatest, least, and equal amounts.
• Think about what the graph is telling you.

Common mistakes to avoid

• Forgetting to read the title
• Mixing up categories
• Counting a bar or X incorrectly
• Forgetting that a pie chart shows parts of one whole

Summary

Data is information that scientists collect. Tables help organize data, and graphs help show data in a way that is easy to understand.

Bar graphs compare groups, line plots show how often numbers happen, and pie charts show parts of a whole. When you read graphs carefully, you can compare data, find patterns, and explain what the data shows.

Identifying Patterns and Trends is an important science skill. Scientists look at information, called data, to learn about the world. Data can be shown in pictures like charts, tables, graphs, and drawings.

When scientists study data, they ask: What do I notice? They look for things that repeat, things that change, and things that do not fit. This helps them make smart guesses and explain what might be happening.

In this lesson, you will learn how to find patterns, trends, results that go together, results that do not match, and simple cause-and-effect ideas.

What is a pattern?

A pattern is something that repeats. In science, a pattern can happen when the same result shows up again and again.

• If a plant in sunlight grows taller every week, that is a pattern.
• If the temperature is warmer every afternoon than every morning for many days, that is a pattern.
• If a magnet always pulls a paper clip, that is a pattern.

Patterns help scientists notice what usually happens.

What is a trend?

A trend is the way something changes over time or across a set of data. A trend may show that something is going up, going down, or staying about the same.

• If a line on a graph goes upward, the data shows an increasing trend.
• If the numbers get smaller, the data shows a decreasing trend.
• If the numbers stay close together, the data shows little or no change.

Patterns repeat. Trends show the direction of change.

What does “results go together” mean?

Sometimes two things seem to change together. For example, when the amount of rain increases, plant growth may increase too. When one thing changes and another thing also changes, we say the results may go together.

This does not always mean one thing definitely caused the other. It means we notice a connection in the data.

What is an anomaly?

An anomaly is a result that does not match the pattern. You can think of it as a point that seems unusual or different.

• If a plant grows 2 cm each week, but one week it grows 0 cm, that may be an anomaly.
• If the class measures the same object many times and one measurement is very different, that may be an anomaly.

An anomaly does not always mean the data is wrong. It could mean there was a mistake, or something special happened that day.

What is cause and effect?

Cause and effect means one thing happens and makes another thing happen. The cause is why something happened. The effect is what happened.

• Cause: A plant gets more water.
• Effect: The plant grows taller.

Scientists use data to look for possible cause-and-effect relationships. They ask, “Did this change lead to that result?”

How to identify patterns and trends

1. Look carefully at the data. Read the table, chart, or graph.
2. Ask what repeats. Do you see the same result again and again?
3. Ask what changes. Are the numbers going up, down, or staying the same?
4. Look for results that go together. When one thing changes, does another thing also change?
5. Find anything unusual. Is there a result that does not fit the rest?
6. Think about cause and effect. What might be making the change happen?

Words that help you talk about data

• Increase: go up
• Decrease: go down
• Same: does not change much
• Repeat: happens again
• Unusual: different from the others

Worked Example 1: Finding a simple pattern

A class measures a bean plant each week.

Week 1: 2 cm
Week 2: 4 cm
Week 3: 6 cm
Week 4: 8 cm

Step 1: Look at the numbers. The plant heights are 2, 4, 6, and 8.

Step 2: Ask what repeats. Each week, the plant grows 2 cm more.

We can show that with simple math:

$$4-2=2$$

$$6-4=2$$

$$8-6=2$$

Answer: The pattern is that the plant grows 2 cm each week. The trend is upward because the plant is getting taller over time.

Worked Example 2: Finding a trend in weather data

A student records the temperature at noon for 5 days.

Day 1: 60°F
Day 2: 63°F
Day 3: 65°F
Day 4: 68°F
Day 5: 70°F

What do we notice? The temperature gets warmer each day.

The numbers are increasing:

$$60<63<65<68<70$$

Answer: The data shows an increasing trend. A good science sentence is: “The noon temperature went up over the 5 days.”

Worked Example 3: Finding an anomaly

A class tests how many minutes an ice cube takes to melt in the sun on similar days.

Test 1: 10 minutes
Test 2: 11 minutes
Test 3: 3 minutes
Test 4: 10 minutes
Test 5: 11 minutes

Step 1: Look for the repeated results. Most of the results are about 10 or 11 minutes.

Step 2: Find the unusual result. The 3-minute result is very different.

Answer: 3 minutes is the anomaly. It does not fit the pattern of the other tests.

What might explain it? Maybe the ice cube was smaller. Maybe it was placed in a hotter spot. Maybe there was a measuring mistake.

Worked Example 4: Looking for cause and effect

A student grows two plants for 3 weeks.

• Plant A gets water every day.
• Plant B gets water only one day each week.

After 3 weeks:

• Plant A is 12 cm tall.
• Plant B is 5 cm tall.

What do we notice? The plant that got more water grew taller.

Possible cause: getting more water

Possible effect: growing taller

Answer: The data suggests a cause-and-effect relationship: more water may help the plant grow more.

Important note: Scientists try to be careful. They ask if anything else was different too, like sunlight or soil. That helps them make a fair comparison.

How graphs and tables help

Data visualizations are pictures of data. They help us see patterns and trends faster.

• Tables organize numbers in rows and columns.
• Bar graphs help compare amounts.
• Line graphs help show change over time.
• Picture charts help us count and compare.

When you read a graph or table, remember to check:

• the title
• the labels
• the numbers
• what is being compared

Questions good scientists ask

• What happens again and again?
• Are the results increasing, decreasing, or staying the same?
• Do two things change together?
• Is there one result that does not fit?
• What might have caused the change?

Be careful when studying data

Sometimes it is easy to rush. Good scientists slow down and look closely.

• Read all the data, not just one part.
• Do not ignore unusual results.
• Compare carefully.
• Use the data to support your answer.

Let’s practice thinking

If bird sightings in a park are 2, 4, 6, and 8 over four mornings, what do you notice?

• The number of birds increases.
• There is a pattern of adding 2.
• The trend goes upward.

If a plant usually grows 1 cm each day, but one day it shrinks, what should you ask?

• Was that an anomaly?
• Was there a mistake in measuring?
• Did something different happen that day?

Summary

Identifying patterns and trends means studying data to see what repeats, what changes, and what stands out. A pattern repeats. A trend shows whether data goes up, down, or stays the same.

Scientists also look for results that go together, unusual results called anomalies, and simple cause-and-effect relationships. When you read a table, chart, or graph carefully, you can use data to make smart science ideas.

Developing Scientific Models means making something that helps us show and think about how something in nature works.

A model is not the real thing. A model is a copy, a picture, or an idea that helps us learn.

Scientists use models all the time. They make models to explain things that are too big, too small, too far away, or too hard to hold.

First graders can be scientists too. You can draw a model, build a model, or use your hands and words to show a model.

Introduction: What Is a Model?

A model is something that stands for something else.

• A drawing of a plant is a model of a plant.
• A toy car is a model of a real car.
• A ball-and-stick shape can be a model of how something is put together.

Models help us answer questions like:

• What does it look like?
• What parts does it have?
• How does it move or change?
• How are the parts connected?

Main Teaching Point 1: There Are Different Kinds of Models

Scientists use different kinds of models. You can too.

• Visual models are pictures, drawings, and diagrams.
• Physical models are things you can build and touch.
• Idea models are simple ways to explain how something works using words and thinking.

A visual model might be a drawing of the Sun, cloud, and rain.

A physical model might be a paper plant with roots, stem, leaves, and flower.

An idea model might be: “Plants need water and sunlight to grow.” That idea helps explain what happens.

Main Teaching Point 2: A Good Model Shows Important Parts

A good model does not have to show everything. It should show the important parts.

If you make a model of a plant, the important parts might be:

• roots
• stem
• leaves
• flower

You may also show what the plant needs:

• sunlight
• water
• soil

Your model helps other people see the parts and understand how they work together.

Main Teaching Point 3: Models Can Show Things That Are Hard to See

Some things are too far away, like stars.

Some things change over time, like a seed growing into a plant.

Some things move very slowly or very quickly.

A model can help us show these things in a simple way.

For example, a drawing can show the steps of plant growth:

1. seed
2. sprout
3. small plant
4. big plant

This model helps us understand change over time.

Main Teaching Point 4: Models Are Helpful, but They Are Not Perfect

A model is useful, but it is not exactly the same as the real thing.

A toy bird cannot fly like a real bird.

A drawing of the Moon does not glow in the sky.

A paper flower does not grow.

This means models have limits. A limit is something the model cannot do or show.

When we use a model, we should ask:

• What does this model show well?
• What does this model not show?

Main Teaching Point 5: Models Can Be Big or Small

Sometimes a model is smaller than the real thing.

• A toy bus is smaller than a real bus.
• A drawing of a tree is smaller than a real tree.

Sometimes a model can make something look bigger so we can notice the parts more easily.

For example, a large drawing of an ant can help us see its body parts.

So, a model may change size to help us learn.

Main Teaching Point 6: We Can Use Models to Share Our Ideas

Scientists make models to share their thinking with other people.

You can use a model to explain what you know.

You might:

• draw a picture
• label the parts
• build with paper or blocks
• point to each part and explain it

When you share your model, use clear words like:

• “This part is the stem.”
• “These leaves help the plant.”
• “The sun gives light.”
• “My model shows how the seed grows.”

How to Make a Simple Scientific Model

1. Pick something to study. Example: a plant, the weather, or an animal.
2. Think about the important parts. What should your model show?
3. Choose the kind of model. Will you draw it or build it?
4. Make your model. Add the important parts.
5. Explain your model. Tell what it shows.
6. Think about its limit. What is missing? What can it not do?

Worked Example 1: Drawing a Plant Model

Question: How can we make a model of a plant?

Step 1: Think about the important parts. A plant has roots, a stem, leaves, and maybe a flower.

Step 2: Draw the plant.

Step 3: Add sunlight, water, and soil because plants need these to live and grow.

Step 4: Explain the model: “My model shows the parts of a plant and what it needs.”

What the model shows well: the parts and what the plant needs.

What the model cannot do: it cannot really grow.

Worked Example 2: Building a Weather Model

Question: How can we make a model to show a rainy day?

Step 1: Pick the important parts: cloud, raindrops, sky, and ground.

Step 2: Use cotton for clouds and blue paper strips for rain.

Step 3: Put the cloud above the ground and hang the rain below the cloud.

Step 4: Explain the model: “My model shows rain falling from clouds.”

What the model shows well: where the rain comes from.

What the model cannot do: it does not make real rain.

Worked Example 3: Showing How a Seed Grows

Question: How can we model change over time?

Step 1: Draw four boxes.

Step 2: In box 1, draw a seed.

Step 3: In box 2, draw a small sprout.

Step 4: In box 3, draw a little plant with leaves.

Step 5: In box 4, draw a bigger plant.

Step 6: Explain the model: “My model shows the steps of plant growth.”

What the model shows well: the order of growth.

What the model cannot do: it does not show every day of growth.

Worked Example 4: Comparing a Toy Animal to a Real Animal

Question: Is a toy animal a good model?

Look closely: A toy dog may have four legs, ears, eyes, and a tail.

That is helpful because it shows body parts.

But think about the limit: The toy dog cannot bark, run, eat, or grow.

Conclusion: Yes, it is a useful model for showing shape and parts, but not for showing everything a real dog can do.

Tips for Making Strong Models

• Keep it simple.
• Show the most important parts.
• Use labels if you can.
• Use colors and shapes to make ideas clear.
• Be ready to say what your model shows.
• Be honest about what your model does not show.

Let’s Practice Thinking Like a Scientist

If you made a model of the Sun and Earth, you would not need every tiny detail. You would show the parts that help explain your idea.

If you made a model of a butterfly life cycle, you could show the steps in order.

If you made a model of a tree in winter and spring, you could show how it changes.

That is what scientists do. They use models to help people see and understand.

Summary

A scientific model is a picture, object, or idea that helps us learn about something real.

Models can show parts, steps, and changes. They can help us understand things that are hard to see or hard to hold.

Good models show important information, but they are not perfect. Every model has limits.

When you make a model, think about what it shows, how it helps, and what it cannot do. That is how you begin to think like a scientist.

Formulating Hypotheses and Predictions

Scientists ask questions about the world. Then they try to find answers by observing, testing, and thinking carefully.

One important science skill is learning how to make a hypothesis and a prediction. These help us think about what might happen before we do an experiment or investigation.

In this lesson, you will learn what hypotheses and predictions are, how they are different, and how to make your own.

What Is a Prediction?

A prediction is a smart guess about what will happen next. It is not just any guess. It is based on things you already know, things you have seen, or patterns you notice.

For example, if dark clouds fill the sky, you might predict that it will rain. You are using what you have seen before to make a good guess.

What Is a Hypothesis?

A hypothesis is an idea you can test. It explains what you think will happen and why.

A hypothesis often uses this form:

If one thing changes, then something else will happen, because of a reason.

Here is an example:

If a plant gets more sunlight, then it will grow taller, because plants need sunlight to make food.

This is testable. You can put one plant in more sunlight and another in less sunlight, then compare them.

Prediction and Hypothesis: How Are They Different?

• Prediction: tells what you think will happen.
• Hypothesis: tells what you think will happen and why.

Both are useful in science. A prediction is often shorter. A hypothesis gives a reason and can be tested.

Why Do Scientists Make Hypotheses and Predictions?

Scientists do not just start testing without thinking. They use what they already know to make a plan.

• They help scientists stay focused.
• They help scientists decide what to test.
• They help scientists compare what they thought with what really happened.
• They help scientists learn from results.

Where Do Good Predictions Come From?

Good predictions come from prior knowledge and observed patterns.

Prior knowledge means things you already know. Maybe you know ice melts when it gets warm. Then you can predict that an ice cube left in the sun will melt.

Observed patterns are things that happen again and again. If you notice that a ball rolls farther on a smooth floor than on grass, you can use that pattern to make a prediction.

How to Make a Good Prediction

1. Look carefully at what you observe.
2. Think about what you already know.
3. Notice any patterns.
4. Make a statement about what will happen.

Try to use words that are clear and specific.

Instead of saying, Something will happen to the plant, say, The plant by the window will grow taller in one week.

How to Make a Good Hypothesis

1. Ask a question you can test.
2. Choose one thing to change.
3. Think about what might happen.
4. Give a reason based on what you know.
5. Say it as an if-then-because sentence.

For example, question: Does water amount change plant growth?

Hypothesis: If a plant gets more water, then it will grow taller, because plants need water to grow.

What Makes a Hypothesis Testable?

A testable hypothesis is one you can check by doing something and observing the result.

For example:

• Testable: If a toy car is pushed harder, then it will roll farther, because a stronger push makes it move more.
• Not testable: If I wish really hard, my plant will be the happiest.

The second one is not easy to measure or test in a science investigation.

Use Only One Change at a Time

When scientists test an idea, they try to change just one thing. This helps them know what caused the result.

Imagine you are testing plant growth. If you change the sunlight, water, and soil all at once, you will not know which change made the difference.

So it is better to change one thing, like sunlight, and keep the other things the same.

Words That Can Help

• I observe...
• I notice...
• I know that...
• I predict...
• If... then... because...

These sentence starters can help you explain your thinking like a scientist.

Worked Example 1: Simple Prediction

Situation: Maya puts an ice cube on a plate outside on a hot day.

What does Maya already know? Ice melts when it gets warm.

Prediction: The ice cube will melt.

Why is this a good prediction? It is based on prior knowledge. Maya has seen ice melt before.

Worked Example 2: Prediction from a Pattern

Situation: Jordan notices that every morning this week, the school flag blows strongly when the trees are bending in the wind.

Today, Jordan sees the trees bending again.

Prediction: The school flag will blow strongly today.

Why is this a good prediction? Jordan used a pattern he observed many times.

Worked Example 3: Writing a Hypothesis

Question: Will a bean seed grow better in sunlight or in a dark closet?

Think: Plants need sunlight to make food.

Hypothesis: If a bean seed is grown in sunlight, then it will grow better than a bean seed in a dark closet, because plants need sunlight to make food.

How could we test it?

• Plant two bean seeds.
• Give both the same amount of water.
• Use the same kind of soil.
• Put one in sunlight and one in a dark place.
• Observe what happens.

This is a strong hypothesis because it tells what will happen and gives a reason.

Worked Example 4: Choosing the Better Hypothesis

Question: Does the length of a ramp change how far a toy car rolls?

Which is better?

• A: The car will do something different.
• B: If the ramp is longer, then the toy car will roll farther, because it has more distance to move down the ramp.

Better choice: B

Why? It is clear, specific, and testable. It says what changes, what might happen, and why.

How to Check Your Own Work

After you write a prediction or hypothesis, ask yourself these questions:

• Did I use something I already know or a pattern I observed?
• Did I clearly say what I think will happen?
• Did I give a reason? (for a hypothesis)
• Can this be tested?
• Did I change only one thing?

Common Mistakes to Avoid

• Making a random guess with no reason.
• Being too unclear, like saying it will be better without saying how.
• Changing many things at once in a test.
• Writing a hypothesis that cannot be tested.

Science in Real Life

You use predictions every day, even when you do not notice.

• If the sidewalk is wet, you may predict it rained.
• If you forget to water a plant, you may predict it will droop.
• If you kick a ball harder, you may predict it will go farther.

Scientists do this too. They observe, think, and make careful guesses based on evidence.

Let’s Practice

Example question 1: A student puts one paper towel in water and leaves another dry. What could the student predict?

Possible answer: The paper towel in water will get wet and softer than the dry one.

Example question 2: What is a hypothesis about sound and a drum?

Possible answer: If I hit the drum harder, then it will make a louder sound, because a harder hit makes stronger vibrations.

Example question 3: A student saw that seeds near the window grew taller than seeds on a shelf. What prediction could the student make for the next seed?

Possible answer: A new seed placed near the window will grow taller than a seed placed on the shelf.

Brief Summary

A prediction is a smart guess about what will happen. A hypothesis is a testable idea that says what will happen and why.

Good predictions and hypotheses use prior knowledge and observed patterns. They are clear, specific, and testable.

When you think like a scientist, you do not just guess. You use what you know, notice patterns, and explain your ideas clearly.

Experimental Design: Fair Tests

Scientists ask questions and do experiments to learn about the world. But for an experiment to give a good answer, it must be a fair test.

A fair test means you change only one thing at a time and keep the other things the the same. This helps you know what caused the result.

For example, if you want to know whether a plant grows better in sunlight or shade, you should change only the light. The plants should get the same water, the same kind of soil, and the same size pot. Then you can tell if light made the difference.

If you change many things at once, it is hard to know which thing caused what happened. That is why fair tests are so important in science.

Main Idea: Change One Thing

In a fair test, the one thing you change is the thing you are testing. Everything else should stay the same.

• Change one thing: This is what you want to test.
• Keep the rest the same: These are the conditions that should not change.
• Watch what happens: This is the result you observe and measure.

You do not need big, hard words to understand this. Just remember: one change, same rest, watch results.

Why Fair Tests Matter

Fair tests help scientists answer questions clearly. They make results easier to trust.

• They help us know why something happened.
• They help us compare results.
• They help us make careful choices based on evidence.

What Stays the Same?

When you do a fair test, you should think carefully about all the parts of the experiment. Ask yourself, “What should stay the same so my test is fair?”

Here are some things that often stay the same:

• amount of water
• amount of light
• size of container
• kind of material used
• length of time
• place where the test happens

If these things change too, the test may not be fair.

What Do We Observe?

After changing one thing, we look for the result. We may observe with our eyes, or we may measure with simple tools.

• Which plant is taller?
• Which ice cube melts faster?
• Which paper airplane flies farther?

Observations can be words, numbers, pictures, or simple charts.

Steps for Making a Fair Test

1. Ask a question.
   Example: Which paper towel soaks up more water?
2. Choose one thing to change.
   Example: the brand of paper towel.
3. Keep other things the same.
   Example: same amount of water, same size paper towel pieces, same time.
4. Do the test carefully.
5. Observe and record what happens.
6. Use the results to answer the question.

Worked Example 1: Plant Growth

Question: Do plants grow better in sunlight or in shade?

To make this a fair test, we change only one thing: the amount of light.

• Plant A is in sunlight.
• Plant B is in shade.

What should stay the same?

• same kind of plant
• same size pot
• same soil
• same amount of water
• same number of days

Then we measure the plants. If Plant A grows taller, we can say sunlight helped more in this test.

This is fair because only the light changed.

Worked Example 2: Ice Melting

Question: Does ice melt faster in the sun or in the shade?

We change only one thing: where the ice is placed.

• Ice cube 1 goes in the sun.
• Ice cube 2 goes in the shade.

What should stay the same?

• same size ice cubes
• same kind of plate
• same starting time
• same place outside except for sun or shade

If one ice cube is bigger, the test is not fair. Bigger ice may melt more slowly, so we would not know if the sun or the size caused the change.

Worked Example 3: Paper Airplanes

Question: Does a larger paper airplane fly farther than a smaller one?

We change only one thing: the size of the paper airplane.

What should stay the same?

• same kind of paper
• same person throwing
• same throwing place
• same way of folding, as much as possible
• same number of throws

Then we measure how far each plane flies. We can compare the distances.

If one plane is made from thicker paper and the other is made from thinner paper, that would not be fair. Then size and paper type both changed.

Worked Example 4: Which Sponge Holds More Water?

Question: Which sponge holds more water?

We change only one thing: the type of sponge.

What should stay the same?

• same size sponge pieces
• same amount of time in water
• same bowl of water
• same way of squeezing or not squeezing

If Sponge A is tiny and Sponge B is big, the test is not fair. The bigger sponge may hold more water just because it is bigger.

How to Tell if a Test Is Fair

You can ask these simple questions:

• Did I change only one thing?
• Did I keep the other things the same?
• Did I observe or measure the result carefully?

If the answer is yes to all three, your test is probably fair.

Example of an Unfair Test

A student wants to know which plant food helps plants grow taller.

But the student does this:

• Plant 1 gets one kind of plant food.
• Plant 2 gets a different plant food.
• Plant 1 is in sunlight.
• Plant 2 is in shade.
• Plant 1 gets more water.

This is not a fair test. Too many things changed.

To fix it, the student should keep the sunlight and water the same for both plants. Then the only change would be the kind of plant food.

Using Simple Numbers

Sometimes scientists use numbers to compare results. For example, if one plant grows to 8 inches and another grows to 5 inches, we can compare them.

We can even find how much more one grew:

$$8 - 5 = 3$$

The first plant grew 3 inches more.

Numbers can help us explain what happened in a fair test.

Tips for Young Scientists

• Read the question carefully.
• Decide what one thing you will change.
• Make a list of what must stay the same.
• Be careful and honest when you observe.
• Record what happens with words, pictures, or numbers.

Brief Summary

A fair test changes only one thing at a time. All the other conditions stay the same. Then we observe what happens and use the results to answer a question. Fair tests help scientists learn what really caused a change.

Procedural Adherence and Replication means following directions carefully and writing down each step so someone else can do the same investigation.

Scientists do this because they want their work to be fair, clear, and repeatable. If people follow the same steps, they can check if they get the same results.

In science, a procedure is a list of steps for an investigation. Procedural adherence means sticking to those steps. Replication means doing the investigation again the same way.

When scientists replicate an investigation, they are asking, “If I do the same thing, will I get the same kind of result?” This helps them know if the results are trustworthy.

Why following steps matters

• It keeps the investigation fair.
• It helps everyone do the same test.
• It makes results easier to compare.
• It helps us find mistakes.
• It lets other people learn from the investigation.

If one person skips a step, changes the amount, or uses different tools, the results may change. Then it is hard to know what caused the change.

How to make a good procedure

1. Write the steps in order.
2. Use clear words.
3. Include amounts, like how much or how many.
4. Include time, like how long to wait.
5. Name the tools and materials.
6. Make sure another person could follow it.

Good procedures are like good directions for a game or a recipe. If the directions are missing, people may all do different things.

What should be written down?

• The materials used
• Each step in order
• Amounts, such as 1 cup or 3 drops
• Times, such as wait 5 minutes
• What was observed
• The results

Example 1: Growing a bean seed

Let’s say a class wants to test how a bean seed grows.

1. Put 1 bean seed in a cup with soil.
2. Pour 10 spoonfuls of water into the cup.
3. Place the cup by a sunny window.
4. Water it with 10 spoonfuls every morning.
5. Measure the plant every 2 days.

This is a better procedure than saying, “Plant a seed and water it sometimes.” The better procedure gives clear steps, amounts, and time.

If another class follows the same bean seed steps, they can replicate the investigation. Then both classes can compare what happened.

Worked Example 1

Question: Which procedure is easier to replicate?

• A. “Put a plant somewhere bright and give it water.”
• B. “Put 1 plant on a sunny windowsill and give it 5 spoonfuls of water every morning for 7 days.”

Answer: B is easier to replicate.

Why? It tells exactly where to put the plant, how much water to use, and how often to water it. Another person can follow the same steps.

Example 2: Melting ice cubes

A group wants to see where ice melts faster.

1. Get 2 ice cubes that are the same size.
2. Put 1 ice cube in the sun.
3. Put 1 ice cube in the shade.
4. Check them every 2 minutes.
5. Write down which one melts first.

This procedure is clear because it uses the same kind of ice cube and tells where to place them and when to check them.

If one student uses a big ice cube and another uses a small one, the test is no longer the same. That makes replication harder.

Worked Example 2

Question: A student wrote these steps:

1. Get some ice.
2. Put it somewhere warm.
3. Watch it.

What details are missing?

Answer: The steps are missing important details.

• How many ice cubes?
• What size are they?
• Where is “somewhere warm”?
• How long should we watch?
• How often should we check?

Why does that matter? Without these details, different people may do different tests and get different results.

Following steps carefully

Sometimes students have good procedures, but they do not follow them exactly. This can change the results.

For example, if the procedure says to use 5 spoonfuls of water, but one student uses 8 spoonfuls, the test is different. Even a small change can matter.

That is why scientists try to be careful, honest, and neat when they do investigations.

Worked Example 3

Question: Two students are testing paper towels. The procedure says, “Pour 1 small cup of water on each paper towel.”

Student 1 pours 1 small cup. Student 2 pours 2 small cups.

Can their results be compared fairly?

Answer: No.

Why? They did not follow the same procedure. Student 2 changed an important step, so the test was not fair.

How replication helps

When a test is repeated the same way many times, scientists can see if the results stay similar. If they do, the results are stronger.

For example, if 3 groups do the same seed test and all 3 groups see the plants grow toward sunlight, that gives more support to the result.

Replication does not always mean the results will be exactly the same every time. But if the steps are the same, the results should be close or show the same pattern.

Worked Example 4

Question: Three groups test which toy car rolls farther on the floor. They all use the same kind of car, the same ramp, and the same starting line. Is this good for replication?

Answer: Yes.

Why? The groups are using the same materials and the same steps. That makes it easier to check if the results match.

Tips for students during science investigations

• Read all the steps before starting.
• Do the steps in the correct order.
• Do not skip steps.
• Do not change amounts unless your teacher says to.
• Write down what you did and what you saw.
• Use neat labels and clear notes.

Let’s think about a recipe

A science procedure is a lot like a recipe for cooking. If the recipe says to add 2 cups of flour, but someone adds 4 cups, the food may not turn out right.

Science works the same way. Clear directions and careful following help people get results they can trust.

Summary

A procedure is a set of steps for an investigation. Procedural adherence means following those steps carefully. Replication means repeating the investigation the same way.

When scientists write clear steps and follow them exactly, other people can repeat the work and check the results. This helps make science fair, careful, and trustworthy.

Constructing Evidence-Based Claims is a way scientists explain what they found out.

In science, it is not enough to say, “I think so.” Scientists need to tell what they think, what they observed, and how the observations support the idea.

A helpful way to do this is called CER. CER stands for Claim, Evidence, and Reasoning.

When you use CER, you answer a science question in a clear and careful way.

What is a claim?

A claim is the answer to a question. It tells what you think is true based on what you learned.

For example, if the question is, “Did the plant in sunlight grow taller than the plant in shade?” a claim could be: Yes, the plant in sunlight grew taller.

What is evidence?

Evidence is the information that supports the claim. In science, evidence often comes from observations, measurements, or data from an investigation.

Evidence should be things you saw, counted, measured, or recorded. Good evidence is not just a guess.

• Observations: “The ice melted.”
• Measurements: “The plant grew 4 centimeters.”
• Counts: “There were 12 pill bugs under the wet paper and 3 under the dry paper.”

What is reasoning?

Reasoning explains why the evidence supports the claim. It connects the data to the science idea.

Reasoning can sound like this: “Because plants need sunlight to make food, the plant with more sunlight grew more.”

You can think of CER like building a strong bridge:

• The claim is your main idea.
• The evidence is the strong support underneath it.
• The reasoning connects them together.

Why do scientists use CER?

Scientists use CER so their ideas are clear and supported. This helps other people understand their thinking.

It also helps scientists be fair. Instead of choosing an answer just because they like it, they look at the evidence first.

How to write a CER response

1. Read or listen to the question carefully.
2. Make a claim that answers the question.
3. Find evidence from the investigation, chart, or observations.
4. Add reasoning to explain how the evidence supports the claim.

Helpful question starters

• Claim: “I claim that…” or “The results show that…”
• Evidence: “I know this because…” or “The data showed…”
• Reasoning: “This supports my claim because…” or “This makes sense because…”

What good evidence looks like

Good evidence is specific. It includes details from the investigation.

Instead of saying, “It grew a lot,” you can say, “It grew from 6 cm to 10 cm, so it grew 4 cm.”

We can show that with math:

$$10 - 6 = 4$$

Be careful: opinions are not evidence

If you say, “I think the blue ball rolled farther because blue is my favorite color,” that is an opinion, not evidence.

But if you say, “The blue ball rolled 8 feet and the red ball rolled 5 feet,” that is evidence.

Worked Example 1: Easy

Question: Which cup of water was warmer?

Observations:

• Cup A temperature: 12 degrees
• Cup B temperature: 18 degrees

Step 1: Claim

Cup B was warmer than Cup A.

Step 2: Evidence

Cup B was 18 degrees. Cup A was 12 degrees.

Step 3: Reasoning

A bigger temperature number means the water is warmer. Since 18 is greater than 12, Cup B was warmer.

Full CER answer: Cup B was warmer than Cup A. The evidence is that Cup B was 18 degrees and Cup A was 12 degrees. This supports the claim because water with a higher temperature is warmer.

Worked Example 2: Medium

Question: Did a seed grow better with water or without water?

Investigation results after 1 week:

• Seed with water: grew 5 cm
• Seed without water: grew 0 cm

Step 1: Claim

The seed grew better with water.

Step 2: Evidence

The seed with water grew 5 cm. The seed without water did not grow.

Step 3: Reasoning

Plants need water to grow. Since the watered seed grew and the seed without water did not, the evidence supports the claim.

Full CER answer: The seed grew better with water. The evidence is that the watered seed grew 5 cm, but the seed without water grew 0 cm. This supports the claim because plants need water to grow.

Worked Example 3: More Challenge

Question: Do pill bugs like wet places better than dry places?

Investigation results:

• Wet side: 14 pill bugs
• Dry side: 4 pill bugs

Step 1: Claim

Pill bugs like wet places better than dry places.

Step 2: Evidence

There were 14 pill bugs on the wet side and only 4 on the dry side.

Step 3: Reasoning

If more pill bugs gather in one place, that shows they prefer that place. Since more pill bugs were on the wet side, the evidence supports the claim that they like wet places better.

Full CER answer: Pill bugs like wet places better than dry places. The evidence is that 14 pill bugs were on the wet side and 4 were on the dry side. This supports the claim because the larger number of pill bugs on the wet side shows that they preferred that environment.

Worked Example 4: Comparing two objects

Question: Which toy car traveled farther down the ramp?

Data:

• Car 1: 9 feet
• Car 2: 6 feet

Step 1: Claim

Car 1 traveled farther than Car 2.

Step 2: Evidence

Car 1 went 9 feet. Car 2 went 6 feet.

Step 3: Reasoning

A greater distance means an object traveled farther. Since 9 is more than 6, Car 1 traveled farther.

Full CER answer: Car 1 traveled farther than Car 2. The evidence is that Car 1 went 9 feet and Car 2 went 6 feet. This supports the claim because 9 feet is a greater distance than 6 feet.

Tips for making strong CER answers

• Answer the question directly in your claim.
• Use real data from the investigation.
• Include numbers when you can.
• Explain the science idea in simple words.
• Do not use opinions as evidence.

Mistakes to avoid

• Claim only: “The sunny plant grew more.” This is incomplete because it has no evidence or reasoning.
• No data: “I know because it looked bigger.” This is weak if no observations or measurements are given.
• Off-topic reasoning: “It grew more because I liked that plant.” This is not scientific reasoning.

How to check your work

After writing your answer, ask yourself these questions:

• Did I clearly answer the question?
• Did I include facts, numbers, or observations?
• Did I explain how the evidence supports my claim?

If you can say “yes” to all three, your CER response is strong.

Mini practice

Question: Which material soaked up more water?

• Paper towel: soaked up 7 spoonfuls
• Wax paper: soaked up 0 spoonfuls

A strong answer could be: The paper towel soaked up more water. The evidence is that it soaked up 7 spoonfuls, while the wax paper soaked up 0 spoonfuls. This supports the claim because a material that soaks up more water is more absorbent.

Summary

Constructing evidence-based claims means using Claim, Evidence, and Reasoning to explain science ideas.

The claim answers the question. The evidence gives facts, observations, or data. The reasoning explains why the evidence supports the claim.

When you use CER, your science thinking becomes clear, strong, and easy for others to understand.

Developing and Using Scientific Models is something scientists do to help them learn about the world.

A model is a simple way to show something real. A model can be a drawing, a diagram, a map, a toy, a chart, or something built with objects.

Scientists use models because some things are too big, too small, too far away, or too hard to watch all at once.

For example, Earth is too big to hold in your hands, but a globe is a model of Earth. An ant is small, but a big drawing of an ant can help us study its body parts. The solar system is very far away, so a picture or ball model can help us understand it.

Models do not show everything perfectly. They are meant to help us think, explain, and predict.

Why do scientists use models?

• To show things that are hard to see directly
• To explain how something looks or works
• To share ideas with other people
• To make careful predictions
• To test ideas in a simple way

Different kinds of models

There are many kinds of scientific models. In 3rd Grade, it helps to think about three main kinds.

1. Physical models — objects you can build or touch

Examples: a globe, a model skeleton, a clay volcano, or balls showing the Sun, Earth, and Moon.

2. Visual models — pictures, drawings, diagrams, or maps

Examples: a labeled plant diagram, a life cycle picture, a weather map, or a drawing of the water cycle.

3. Math models — numbers, charts, or simple equations that help explain something

For example, if a plant grows 2 centimeters one week and 2 more centimeters the next week, we can use numbers to model the growth:

Week 1: \(2\) cm
Week 2: \(2 + 2 = 4\) cm

This number pattern helps us understand the plant’s growth.

What makes a good model?

A good model should be clear and helpful. It should show the most important parts of the real thing.

• It includes important details
• It is neat and easy to understand
• Its labels match the real object or system
• It helps answer a question or explain an idea

For example, if you make a model of a flower, it should show important parts like the petals, stem, leaves, and roots. It does not need to show every tiny bump or line.

Models are not the real thing

This is very important: a model is like the real thing, but it is not the real thing.

A globe looks like Earth in shape, but it is much smaller. A drawing of the Moon may show craters, but it does not glow or move through space. A diagram of a bird’s life cycle shows the stages, but it is only a picture.

Because models are simpler than real things, they have limits. A limit is something a model cannot show well.

Here are some examples of limits:

• A toy car model may show shape, but it does not drive like a real car
• A map shows where places are, but it does not show the real trees, smells, or sounds
• A drawing of the solar system may show the planets, but not their true sizes and distances

How to make a scientific model

You can follow simple steps to build a useful model.

1. Ask: What am I trying to show?
2. Choose: Will I use a drawing, an object, or numbers?
3. Include: Add the most important parts
4. Label: Name the parts clearly
5. Explain: Tell how the model matches the real thing
6. Check: Ask, “What does my model show well? What does it not show?”

Using models to learn

Scientists do not just make models. They also use models.

When scientists use a model, they may:

• Study parts of a system
• Compare one thing to another
• Explain what they notice
• Share ideas with others
• Make a prediction about what may happen next

For example, a weather map can help people predict if rain is coming. A plant life cycle model can help students explain how a seed becomes a plant.

Worked Example 1: A model of Earth

Question: Why would a scientist use a globe instead of the real Earth?

Think: Earth is huge. We cannot pick it up and turn it around to look at all sides easily.

Model: A globe is a physical model of Earth.

What it shows well:

• Earth is round like a sphere
• Land and water are in different places
• You can find continents and oceans

What it does not show well:

• The real size of mountains and buildings
• Daily weather in each place
• Every small detail on Earth

Answer: A scientist uses a globe because it is a smaller, easier way to study the shape and surface of Earth.

Worked Example 2: A plant diagram

Question: A class is learning about plant parts. Should they use a labeled drawing of a plant as a model?

Think: A visual model can help us see and name important parts.

Model: A drawing with labels: flower, leaves, stem, roots.

Why it helps:

• It clearly shows the main plant parts
• It helps students remember the names
• It is easier to study than looking at many different real plants

Answer: Yes. A labeled drawing is a good visual model because it shows the important plant parts clearly.

Worked Example 3: A solar system model

Question: A student makes a solar system with foam balls. The Sun is one ball, and each planet is a smaller ball. Is this a model? What can it teach?

Think: The solar system is very large and far away. A physical model can help us picture it.

What the model shows well:

• There is one Sun and many planets
• The planets are separate objects
• The planets can be placed in order

What the model may not show well:

• The true distances between planets
• The real planet sizes
• How planets move over time

Answer: Yes, it is a model. It can teach the order of the planets and that they are part of one system around the Sun.

Worked Example 4: A simple math model

Question: A student measures a bean plant each week. In week 1 it is \(3\) cm tall. In week 2 it is \(5\) cm tall. In week 3 it is \(7\) cm tall. How can numbers be a model?

Think: The numbers show a pattern in the plant’s growth.

Data:

• Week 1: \(3\) cm
• Week 2: \(5\) cm
• Week 3: \(7\) cm

The plant grows by \(2\) cm each week.

We can show the pattern like this:

$$3,\ 5,\ 7$$

or

$$3 + 2 = 5 \quad \text{and} \quad 5 + 2 = 7$$

Answer: The numbers make a math model because they help us see and explain the growth pattern.

Tips for choosing the best model

Different questions need different models. Ask yourself:

• Do I need to show shape? Use a physical model.
• Do I need to label parts? Use a visual model.
• Do I need to show change with numbers? Use a math model.

Sometimes scientists use more than one model. For example, they might use a drawing of a butterfly life cycle and also a chart of how many days each stage lasts.

Common mistakes to avoid

• Adding too many details so the model becomes confusing
• Forgetting labels
• Thinking the model is exactly the same as the real thing
• Leaving out important parts
• Using a model that does not match the question

Let’s remember

A scientific model is a tool for learning. It helps us understand things that may be too big, small, far away, or complex to study easily.

Models can be physical, visual, or math-based. Good models show important parts clearly, but they also have limits.

When you make or use a model, ask: What does this model help me understand? and What does it not show?

Brief Summary

Scientists make models to help explain and study real things. A model can be something you build, draw, or show with numbers. Models are useful because they make hard-to-see things easier to understand, but they are not exactly the same as the real thing.

Scientific Communication and Peer Review

Scientists do more than experiments. They also share what they learn with other people. This is called scientific communication.

When scientists share their ideas, other scientists listen, ask questions, and check the work. This is called peer review. A peer is someone who is also learning or working in the same field. In 3rd grade, your peers are your classmates.

Scientific communication and peer review help us learn the truth as carefully as we can. They help us fix mistakes, notice new ideas, and make our work better.

Why do scientists share their work?

• To tell others what they observed
• To explain what they tested
• To show their evidence
• To hear other ideas and questions
• To improve their thinking

What does good scientific communication look like?

Good scientific communication is clear, organized, and honest. A scientist should say what happened in a way that other people can understand.

When you share your science work, include these parts:

• Question: What are you trying to find out?
• What you did: What steps did you follow?
• Observation: What did you notice with your senses or tools?
• Evidence: What facts, notes, pictures, or measurements support your idea?
• Conclusion: What did you learn?

It is important to tell the truth about your results. Even if your idea was not correct, your observations still matter. In science, being honest is very important.

Ways to communicate in science

• Talking to the class
• Writing in a science notebook
• Making a chart or table
• Drawing a labeled picture
• Creating a poster

What is peer review?

Peer review means that other people look at your work and think about it carefully. They may ask:

• Did the steps make sense?
• Is the evidence clear?
• Does the conclusion match the evidence?
• Is there another way to explain the results?

Peer review is not about being mean. It is about helping. A good peer review is respectful, kind, and focused on the science.

How to give respectful feedback

When you respond to someone else’s science work, use polite words. You can:

• Ask a question: Can you explain how you measured that?
• Point to evidence: I noticed your chart shows the plant grew taller in sunlight.
• Share another idea: I wonder if water also made a difference.
• Suggest a change: Maybe you could label your picture to make it clearer.

How to receive feedback

It is not always easy to hear questions about your work. But in science, questions help us learn. When someone gives feedback, try to:

• Listen carefully
• Stay calm
• Ask questions if you do not understand
• Think about the new idea
• Revise your work if the evidence shows you should

Revise your thinking with new evidence

Sometimes you may think one thing at first, but then new evidence shows something different. In science, that is okay. Good scientists are willing to change their minds when the evidence is strong.

Changing your thinking does not mean you failed. It means you are learning.

Example 1: Sharing clear results

Lena wants to find out whether seeds grow better in sunlight or in shade. She plants two seeds, gives them the same amount of water, and puts one in sunlight and one in shade.

After one week, Lena says, “The seed in sunlight grew to 6 centimeters. The seed in shade grew to 2 centimeters. I think sunlight helped the seed grow more.”

This is good scientific communication because Lena:

• Asked a question
• Explained what she did
• Shared measurements as evidence
• Gave a conclusion that matches the evidence

Example 2: A classmate gives peer review

Marco listens to Lena’s report. He says, “Your results are clear. Did both plants get the same amount of water?”

This is a good peer review question because Marco is checking whether the test was fair. He is not being rude. He is helping Lena think carefully about her experiment.

Lena answers, “Yes, each seed got 10 drops of water every day.” Marco’s question helped Lena make her explanation stronger.

Example 3: Revising with new evidence

Ava thinks bigger rocks always sink faster than smaller rocks. She drops one big rock and one small rock into water. They both sink, but she notices she cannot tell which one was faster.

Her classmate says, “Maybe you need to try again and watch more carefully.” Ava repeats the test several times. She sees that both rocks sink very quickly, and she is not sure the bigger rock is always faster.

Ava revises her thinking. She says, “My first idea may not be right. My evidence does not clearly show that bigger rocks always sink faster.”

That is what scientists do. They use evidence to update their ideas.

Example 4: Making communication clearer

Jamal makes a poster about weather. He writes, “It rained a lot.” His classmates are confused because they want more details.

After peer review, Jamal changes his poster to say, “It rained on 4 days this week.” He also adds a simple chart.

Now his communication is clearer because he used facts instead of only general words.

Helpful sentence starters

You can use these sentence starters when sharing science ideas:

• I observed that...
• My evidence shows...
• I think this happened because...
• One question I have is...
• I would revise my idea by...

Remember these important ideas

1. Scientists share their questions, steps, observations, evidence, and conclusions.
2. Peer review means others check the work and ask thoughtful questions.
3. Feedback should be respectful and helpful.
4. Scientists may revise their thinking when they get new evidence.
5. Clear and honest communication helps everyone learn.

Brief Summary

Scientific communication means sharing science ideas clearly and honestly. Peer review means other people look at the work, ask questions, and help improve it. In science, we listen respectfully, use evidence, and change our thinking when new evidence teaches us something new.

Ethical Treatment of Living Organisms means treating plants, animals, and their homes with care and respect.

When scientists study nature, they do not just ask questions and collect facts. They also make sure they are kind and careful. This is called being ethical. Ethical choices help keep living things safe.

Living organisms are all the living things around us, such as birds, bugs, fish, trees, flowers, and grass. Habitats are the places where living things live, like ponds, forests, gardens, and fields.

In this lesson, you will learn how to observe living things safely, why gentle actions matter, and how to protect habitats during science work.

Why ethical treatment matters

Plants and animals are living things. They need food, water, air, shelter, and safety. If people are rough, loud, or careless, they can hurt living things or damage the places they live.

Scientists want to learn about nature without causing harm. Good scientists try to leave nature the way they found it. They observe carefully and disturb as little as possible.

Main idea 1: Observe first, touch only if needed

The best way to study many living things is to watch them closely. You can use your eyes, ears, or simple tools like a hand lens. Watching is often safer than touching.

If touching is needed, it should be gentle, quick, and safe. Clean hands, soft movements, and teacher help are important. Some animals should never be touched by children because they may be hurt easily or may not be safe to handle.

• Look quietly before moving closer.
• Use tools like magnifiers or notebooks to learn more.
• Do not grab, squeeze, or chase animals.
• Touch plants and animals only when your teacher says it is okay.

Main idea 2: Respect habitats

A habitat is a living thing's home. It has everything the living thing needs to survive. When we move rocks, pick flowers, break branches, or step on small plants, we can change that home.

Even small actions can matter. A turned-over rock may have been shelter for insects. A broken plant may lose its leaves and stop growing well. A loud group near a nest may scare parent animals away.

To respect habitats, students should be careful about where they walk and what they move.

• Stay on paths when possible.
• Leave nests, webs, and burrows alone.
• Put back any rock or log only if a teacher says it is okay and exactly where it was.
• Do not pick living flowers or pull leaves from plants just to keep them.
• Take notes or draw pictures instead of taking parts of nature home.

Main idea 3: Cause as little disruption as possible

Disruption means changing what living things are doing or changing their environment. Ethical scientists try to keep disruption small.

For example, if a bird stops eating because people stand too close, the study is causing a problem. If students trample grass near an ant hill, they are changing the habitat. A better choice is to step back, stay quiet, and watch from a distance.

Here are ways to reduce disruption:

• Use quiet voices.
• Move slowly.
• Watch from a safe distance.
• Spend only a short amount of time very close to animals.
• Return anything borrowed from nature right away, if it is safe and allowed by the teacher.

Main idea 4: Keep living things safe and keep yourself safe

Being ethical also means being safe. Some plants may cause itching. Some animals may bite or sting when scared. Students should never touch unknown plants or animals.

Always follow class safety rules. Ask an adult before picking up any living thing. Wash hands after outdoor studies. Use containers only if a teacher says to, and never keep an animal trapped longer than needed.

• Do not taste plants.
• Do not disturb bees, wasps, or other stinging animals.
• Do not go near animal nests or babies.
• Tell the teacher if you find an injured animal.

Main idea 5: Be kind when collecting information

Scientists collect information in many ways. They can count birds, measure plant height, draw leaf shapes, or write what they notice. These are good ways to learn without harming living things.

Sometimes students may want to bring home a flower, feather, or bug. But ethical study means asking, "Do I really need to take this?" Often, the answer is no. A sketch, photo, or note is enough.

Good choices during field studies

1. Look carefully.
2. Stay calm and quiet.
3. Leave habitats mostly unchanged.
4. Touch only when allowed and only gently.
5. Put safety first.
6. Take notes, drawings, or photos instead of taking living things.

Worked Example 1: Watching a butterfly

Situation: Maya sees a butterfly on a flower during a class walk. She wants to get a closer look.

Question: What is the ethical choice?

Think: Butterflies are delicate. Running at the butterfly or grabbing it could hurt it or scare it away.

Answer: Maya should move slowly, stay a little distance away, and observe with her eyes or a hand lens if her teacher says it is okay. She can draw the butterfly in her notebook instead of trying to catch it.

Why this works: She learns about the butterfly while keeping it safe.

Worked Example 2: Finding a rock with bugs under it

Situation: Luis lifts a rock and sees tiny bugs underneath.

Question: What should he do?

Think: The bugs may use the rock as shelter. Leaving the rock moved could change their habitat.

Answer: Luis should observe quickly, tell his teacher what he found, and gently place the rock back exactly as it was if the teacher says it is safe.

Why this works: The bugs keep their shelter, and Luis still gets to learn.

Worked Example 3: Picking flowers for a project

Situation: A group wants real flowers to glue on a poster.

Question: Is this the best ethical choice?

Think: Picking living flowers removes part of a plant and changes the habitat. Other animals may use the flowers too.

Answer: A better choice is to draw the flowers, take photos, or use paper pictures. If the class uses plant parts, it should only be with teacher permission and in a careful way.

Why this works: The class can still complete the project without harming living plants.

Worked Example 4: Seeing a baby bird on the ground

Situation: Jenna sees a baby bird near a tree and wants to help by picking it up.

Question: What should she do?

Think: Touching the bird may scare it or make the situation worse. Children should not handle wild animals on their own.

Answer: Jenna should not pick up the bird. She should step back, keep others away, and tell the teacher or another adult right away.

Why this works: Adults can decide the safest way to help without causing more harm.

Examples of ethical and unethical actions

Ethical actions:

• Drawing a plant instead of picking it.
• Watching ants quietly from the side.
• Using a notebook to record what you see.
• Walking carefully so you do not crush plants.
• Putting nature back the way you found it.

Unethical actions:

• Chasing frogs for fun.
• Pulling leaves off a plant.
• Yelling near a bird nest.
• Keeping a wild animal in a jar for a long time.
• Breaking branches to get a better view.

Questions to ask yourself in nature

• Am I being gentle?
• Am I being quiet?
• Am I leaving this place mostly the same?
• Am I keeping the plant or animal safe?
• Am I following my teacher's safety rules?

Brief Summary

Ethical treatment of living organisms means showing care and respect to plants, animals, and habitats. Good scientists observe closely, disturb as little as possible, and make safe, kind choices. When we study nature gently, we can learn a lot while protecting living things and their homes.