Energy Forms: Light, Sound, and Thermal Dynamics

Sources of Electromagnetic Radiation

Have you ever looked outside and seen the bright Sun? Have you turned on a lamp or watched a screen glow? All of these give off light.

Light is a kind of energy that helps us see. In this lesson, we will learn about where light comes from. Some light comes from nature, and some light is made by people.

Scientists use a big name, electromagnetic radiation, for light energy. For 1st grade, you can think of it as light that travels. We can see some kinds of this light with our eyes.

Main Idea: A source is where something begins. A light source is something that makes its own light.

Things that only bounce light are not light sources. For example, the Moon looks bright, but it does not make its own light. It reflects light from the Sun.

There are two big groups of light sources:

• Natural light sources — found in nature
• Artificial light sources — made by people

1. Natural light sources

Natural light sources are things in nature that make light on their own.

• The Sun — The Sun is our biggest natural light source. It gives Earth light and warmth.
• Fire — Fire can happen in nature, like when lightning starts a forest fire. Fire gives off light and heat.
• Bioluminescence — Some living things can glow. This is called bioluminescence. For example, fireflies glow in the dark.

The Sun is very important because it lights up the daytime sky. Without the Sun, our days would be dark.

Fire is also a source of light. A campfire or a wildfire can glow brightly. Fire gives us both light and heat.

Some animals and sea creatures can make their own light. A firefly is a great example. When it glows, it is a natural light source.

2. Artificial light sources

Artificial light sources are made by people. They help us see when it is dark or when we are indoors.

• Incandescent bulbs — These are light bulbs that glow when turned on.
• LEDs — These are small lights used in lamps, flashlights, and many toys.
• Screens — TV screens, tablet screens, and phone screens give off light.

A lamp with a bulb is an artificial light source because people made it. When you flip the switch, the bulb shines.

LED lights are used in many places. They can be in traffic lights, flashlights, holiday lights, and room lights.

Screens are also light sources. A tablet or TV does not just bounce light. It makes light so you can see pictures and words.

How can we tell if something is a light source?

Ask this question: Does it make its own light?

• If yes, it is a light source.
• If no, it is not a light source.

For example:

• The Sun makes its own light. Yes, it is a light source.
• A light bulb makes its own light when turned on. Yes, it is a light source.
• The Moon does not make its own light. No, it is not a light source.
• A mirror does not make light. It only reflects light. No, it is not a light source.

Natural or artificial?

Once we know something is a light source, we can sort it into a group.

• If it comes from nature, it is natural.
• If people made it, it is artificial.

Here is a helpful way to think about it:

1. Does it make its own light?
2. If yes, is it from nature or made by people?

Worked Example 1

Question: Is the Sun a natural light source or an artificial light source?

Step 1: Does the Sun make its own light? Yes.

Step 2: Is the Sun from nature or made by people? It is from nature.

Answer: The Sun is a natural light source.

Worked Example 2

Question: Is a lamp bulb a natural light source or an artificial light source?

Step 1: Does the bulb make its own light when it is on? Yes.

Step 2: Is the bulb from nature or made by people? It is made by people.

Answer: A lamp bulb is an artificial light source.

Worked Example 3

Question: A firefly glows at night. Is it a light source?

Step 1: Does the firefly make its own light? Yes, it glows.

Step 2: Is it from nature or made by people? It is from nature.

Answer: Yes, a firefly is a natural light source.

Worked Example 4

Question: Is the Moon a natural light source?

Step 1: Does the Moon make its own light? No.

Step 2: It only reflects light from the Sun.

Answer: No, the Moon is not a light source.

Let’s compare

• Natural light sources: Sun, fire in nature, fireflies
• Artificial light sources: light bulbs, LEDs, screens
• Not light sources: Moon, mirror, book, chair

Why light sources matter

Light sources help us in many ways. The Sun helps plants grow and helps us see during the day. Lamps help us read at night. Screens show us pictures and words.

Some light sources also give off heat. The Sun and fire are good examples. That is why they can feel warm or hot.

Summary

A light source is something that makes its own light. Some light sources are natural, like the Sun, fire, and fireflies. Some light sources are artificial, like incandescent bulbs, LEDs, and screens.

To decide if something is a light source, ask: Does it make its own light? If it does, then ask: Is it natural or artificial?

Light helps us see. We see things when light shines on them and then comes to our eyes.

Light can come from the Sun, a lamp, a flashlight, or a candle. These are called light sources because they make light.

Light moves in straight lines. It keeps going straight until it hits something, like a wall, a book, or a toy.

When light hits an object, the light can bounce off the object. This bouncing light can go into our eyes. Then we can see the object.

If there is no light, we cannot see the object well. That is why a dark room is hard to see in.

Our eyes need light to help us see. Light goes from a light source, to an object, and then into our eyes.

Here is the idea in a simple path:

$$\text{light source} \rightarrow \text{object} \rightarrow \text{eyes}$$

Let’s learn the big ideas.

• Light travels straight.
• Light hits an object.
• Light bounces off the object.
• The bounced light goes into our eyes.
• Then we see the object.

Think about a toy bear on a table.

If the room light is on, light travels from the lamp to the toy bear. Then some light bounces off the toy bear and goes into your eyes. Now you can see the toy bear.

If the room is very dark, there is little or no light hitting the toy bear. Then little or no light bounces into your eyes. Now the toy bear is hard to see.

Shadows can help us know that light travels in straight lines.

When an object blocks light, the light cannot go through it. A dark shape forms behind the object. That dark shape is called a shadow.

For example, if you hold your hand in front of a flashlight, the light travels straight until your hand blocks it. A shadow shows up on the wall.

Worked Example 1

Question: Why can you see a book near a lamp?

Step 1: The lamp makes light.

Step 2: The light travels to the book.

Step 3: The light bounces off the book.

Step 4: The bounced light goes into your eyes.

Answer: You can see the book because light from the lamp bounces off the book and enters your eyes.

Worked Example 2

Question: Why is it hard to see your shoes in a dark closet?

Step 1: A dark closet has very little light.

Step 2: Very little light hits your shoes.

Step 3: Very little light bounces into your eyes.

Answer: It is hard to see your shoes because there is not enough light bouncing into your eyes.

Worked Example 3

Question: A flashlight shines on a ball. How do you see the ball?

Step 1: The flashlight is the light source.

Step 2: Light travels in straight lines from the flashlight to the ball.

Step 3: Light bounces off the ball.

Step 4: The bounced light enters your eyes.

Answer: You see the ball because the flashlight light bounces off the ball and goes into your eyes.

Worked Example 4

Question: Why does a shadow happen when you stand in sunlight?

Step 1: Sunlight travels in straight lines.

Step 2: Your body blocks some of the light.

Step 3: The place behind you gets less light.

Answer: A shadow happens because your body blocks light that travels in straight lines.

Let’s look at some everyday examples.

1. Seeing a friend outside: Sunlight shines on your friend. Light bounces off your friend and goes into your eyes.
2. Seeing food on your plate: Kitchen light shines on the food. Light bounces off the food and goes into your eyes.
3. Using a flashlight under a blanket: The flashlight makes light. The light shines on objects, and the bounced light helps you see them.

Remember these important ideas:

• Light comes from a source, like the Sun or a lamp.
• Light travels in straight lines.
• Light must hit an object for us to see it.
• Light bounces off the object and enters our eyes.
• Without light, seeing is hard or not possible.

You can even say the seeing path like this:

light source → object → eyes

When you remember that path, you can explain how we see many things around us.

Brief Summary

Light travels in straight lines from a light source. When light hits an object, it bounces off and can go into our eyes. We see things because light enters our eyes after bouncing off objects. If there is no light, it is hard to see.

Reflection and Absorption

We use light every day. Light helps us see people, toys, books, and the world around us.

When light hits something, two important things can happen. The light can bounce off, or the light can be soaked up.

When light bounces off a surface, we call it reflection.

When light is soaked up by a surface, we call it absorption.

Let’s learn how each one works.

1. Reflection: Light Bounces Off

Reflection happens when light hits a surface and bounces back.

Smooth, shiny surfaces reflect light best. These surfaces make the light bounce in a neat way.

Because the light bounces back neatly, we can sometimes see a clear image. That is why a mirror shows your face.

• Mirror
• Still water
• Shiny metal spoon

These are things that can reflect light.

If a surface is very smooth and shiny, the reflection is easier to see.

2. Absorption: Light Is Soaked Up

Absorption happens when light hits a surface and the surface takes in the light.

Dark surfaces often absorb more light. Rough or textured surfaces also do not reflect light in a clear way.

When light is absorbed, the object can get warmer. The light energy changes to heat.

• A black shirt in the sun
• Dark playground slide
• A rough, dark mat

These things can absorb a lot of light and feel warm.

3. Smooth and Shiny or Dark and Rough?

It helps to think about how a surface looks and feels.

• Smooth and shiny surfaces usually reflect more light.
• Dark surfaces usually absorb more light.
• Rough or textured surfaces do not make clear reflections.

A smooth mirror reflects light very well.

A dark carpet does not reflect light like a mirror. It absorbs much of the light instead.

4. What Do We See?

If light reflects, it can travel to our eyes. Then we can see a bright spot or even a picture, like in a mirror.

If light is absorbed, less light bounces back to our eyes. The object may look darker.

Some objects do a little of both. They reflect some light and absorb some light.

Worked Example 1

Question: Which reflects light better: a mirror or a black T-shirt?

Think: A mirror is smooth and shiny. A black T-shirt is dark and not shiny.

Answer: The mirror reflects light better.

Why: Smooth, shiny surfaces bounce light back neatly.

Worked Example 2

Question: Which will get warmer in bright sunlight: a white shiny cup or a dark rough rock?

Think: Dark and rough surfaces absorb more light.

Answer: The dark rough rock will get warmer.

Why: It absorbs more light, and that light energy becomes heat.

Worked Example 3

Question: You want to see your face. Should you look in a mirror or at a towel?

Think: To see your face, you need a clear reflection.

Answer: You should look in a mirror.

Why: A mirror is smooth and shiny, so it reflects light in a way that makes a clear image. A towel is rough, so it does not.

Worked Example 4

Question: A child touches two objects in the sun: a shiny metal lunch box and a dark mat. Which one is more likely to feel hotter?

Think: Dark surfaces absorb more light.

Answer: The dark mat is more likely to feel hotter.

Why: It absorbs more light energy and changes it to heat.

Try to Remember

1. Reflection means light bounces off.
2. Absorption means light is soaked up.
3. Smooth, shiny surfaces reflect light best.
4. Dark or rough surfaces absorb more light and can get warmer.

Real-Life Examples

• You see yourself in a bathroom mirror because of reflection.
• A black car in the sun can get hot because of absorption.
• A shiny spoon can show a tiny reflection.
• A dark sidewalk can feel warm on a sunny day.

Quick Check

Ask yourself these questions:

• Does the surface look smooth and shiny?
• If yes, it may reflect a lot of light.
• Does the surface look dark or rough?
• If yes, it may absorb more light.

Summary

Light can bounce off objects or be soaked up by them.

When light bounces off, it is called reflection. Mirrors and other smooth, shiny surfaces reflect light well.

When light is soaked up, it is called absorption. Dark and rough surfaces absorb more light and can get warmer.

Now you know why mirrors help us see reflections and why dark objects in the sun can feel hot.

Shadow Formation and Geometry

Have you ever seen your shadow on the ground on a sunny day? A shadow is a dark shape made when light is blocked.

This lesson will help you learn how shadows form and why shadows can look bigger, smaller, longer, or shorter.

What makes a shadow?

Light travels from a light source, like the Sun or a lamp. When something is in the way, the light cannot go through it.

If an object blocks the light, a dark area appears behind it. That dark area is called a shadow.

Three things we need for a shadow

• A light source — like the Sun, a flashlight, or a lamp
• An object — like your hand, a toy, or a book
• A surface — like the ground, a wall, or paper

If one of these is missing, it is hard to see a shadow.

Which objects make strong shadows?

Objects that light cannot pass through are called opaque. Opaque objects make clear shadows.

A book, a chair, and your body are all examples of opaque objects.

Shadow shape

A shadow often has a shape like the object making it. A round ball can make a round shadow. A toy block can make a square or rectangle-like shadow.

Sometimes the shadow shape changes a little if the light shines from a different place. But the shadow still comes from the object blocking the light.

Shadow size can change

Shadows do not always stay the same size. They can get bigger or smaller.

If the light source moves closer to the object, the shadow can look bigger.

If the light source moves farther away from the object, the shadow can look smaller.

We can compare sizes like this:

$$\text{big shadow} > \text{small shadow}$$

Shadow length can change

Shadows can also get longer or shorter.

When light shines from low down, shadows often look long.

When light shines from high up, shadows often look short.

This is why your shadow may look long in the morning or evening and shorter in the middle of the day.

Angle changes the shadow

The angle means the way the light is shining.

If light shines from the side, the shadow stretches out more. If light shines more from above, the shadow stays shorter.

You do not need to measure the angle with numbers yet. You only need to notice that where the light is changes the shadow.

Simple shape ideas in shadows

Geometry means learning about shapes. Shadows can help us see shapes.

• A ball can make a circle-like shadow.
• A box can make a square or rectangle-like shadow.
• A tall object can make a long shadow.
• A short object can make a shorter shadow.

We can compare lengths too:

$$\text{long shadow} > \text{short shadow}$$

Main ideas to remember

1. Light travels from a source.
2. An opaque object blocks the light.
3. A shadow forms on a surface behind the object.
4. Moving the light changes the shadow's size and length.
5. The object's shape helps make the shadow's shape.

Worked Example 1: Finding what makes a shadow

Sara has a flashlight, her hand, and a wall.

Will she be able to make a shadow?

Step 1: Does she have a light source? Yes, the flashlight.

Step 2: Does she have an object to block the light? Yes, her hand.

Step 3: Does she have a surface? Yes, the wall.

Answer: Yes. She can make a shadow on the wall.

Worked Example 2: Bigger or smaller?

Leo shines a flashlight at a toy. First the flashlight is far away. Then he moves the flashlight closer to the toy.

What happens to the shadow?

Step 1: The toy blocks the light.

Step 2: When the flashlight moves closer, the shadow usually gets bigger.

Answer: The shadow gets bigger.

We can say:

$$\text{closer light} \rightarrow \text{bigger shadow}$$

Worked Example 3: Longer or shorter?

A lamp shines on a block.

First the lamp shines from the side. Next the lamp is moved higher up.

How does the shadow change?

Step 1: Light from the side often makes a long shadow.

Step 2: Light from higher up often makes a shorter shadow.

Answer: The shadow changes from longer to shorter.

Worked Example 4: Matching a shape

Mia shines light on a round ball.

Which shadow shape makes the most sense: a circle-like shadow or a rectangle-like shadow?

Step 1: A ball is round.

Step 2: Round objects often make round shadows.

Answer: A circle-like shadow makes the most sense.

Try thinking about these questions

• What happens if you move a flashlight closer to your hand?
• What happens if you move the flashlight farther away?
• What kind of shadow does a book make?
• When is your shadow longer: when light is low or high?

Easy experiment you can do

You can test shadows with a flashlight and a small toy.

1. Point the flashlight at the toy and a wall.
2. Look at the shadow.
3. Move the flashlight closer.
4. See if the shadow gets bigger.
5. Move the flashlight higher or lower.
6. See if the shadow gets shorter or longer.

Be safe and do not shine bright lights into anyone's eyes.

Summary

A shadow forms when light is blocked by an opaque object. You need a light source, an object, and a surface to see a shadow.

Shadows can change size and length. A closer light can make a bigger shadow, and a lower light can make a longer shadow.

Shadows also help us notice shapes, like circles, squares, and rectangles. Watching shadows is a fun way to learn about light and shape.

Sound is made by vibrations. A vibration is a tiny back-and-forth movement. When something vibrates, it can make sound.

We may not always see vibrations, but we can often hear them. A bell, a drum, and our own voices all make sound because something is moving back and forth.

When an object vibrates, it shakes the air around it. The moving air travels to our ears. Then we hear a sound.

So, where does sound come from? Sound comes from matter that is vibrating. Matter means things like strings, paper, metal, wood, water, and even our throat.

Introduction

Have you ever hit a drum, plucked a guitar string, or talked to a friend? All of these make sound. But they only make sound because something is vibrating.

Sound does not just appear by magic. Something has to move back and forth to start the sound. That movement makes the air move too. Then the sound travels through the air to our ears.

Main Teaching Points

1. A vibration is a back-and-forth movement.

You can think of a vibration as a fast shake. It may be big or small. It may be slow or fast. But it is always a kind of movement.

• A ruler can vibrate if it hangs over the edge of a desk and is flicked.
• A drum top vibrates when you tap it.
• A string vibrates when you pluck it.

2. Vibrating objects make sound.

When something vibrates, it pushes the air nearby. The air moves outward. This moving air carries sound.

If the object stops vibrating, the sound stops too. No vibration means no sound.

3. Sound travels through matter.

Sound needs something to travel through, like air, water, or a table. The vibration moves through that material and can reach our ears.

For 1st grade, it is enough to remember: sound travels when vibrations move through air or other things.

4. Our ears hear the sound.

After the vibrating object moves the air, the sound travels to our ears. Our ears help us notice the sound.

5. We can sometimes feel vibrations too.

Put your hand gently on your throat and say, “ahhh.” You may feel a little buzz. That is your throat vibrating to make your voice.

Put your hand on a speaker when music is playing softly. You may feel it shake. That shaking is vibration.

Examples from Everyday Life

• Drum: When you tap a drum, the drum top vibrates and makes sound.
• Bell: When you ring a bell, the bell vibrates and makes a ringing sound.
• Guitar string: When you pluck a string, it vibrates and makes a musical sound.
• Voice: When you talk or sing, part of your throat vibrates and makes sound.
• Clapping: When your hands clap together, they make the air move and create sound.

Worked Examples

Example 1: A drum

Question: Why does a drum make sound when you tap it?

Think: What starts moving?

Answer: The drum top starts to vibrate. The vibration moves the air. The moving air brings sound to our ears.

Example 2: Your voice

Question: Why can you feel your throat move when you talk?

Think: Is something vibrating?

Answer: Yes. Your throat vibrates when you talk. Those vibrations make sound, and that is how your voice is made.

Example 3: A guitar string

Question: A guitar string is plucked. What makes the sound?

Think: Does the string stay still or move?

Answer: The string moves back and forth. That vibration makes the air move. Then we hear the sound.

Example 4: A stopped bell

Question: A bell is ringing. Then you hold it still. What happens to the sound?

Think: What happens when the vibration stops?

Answer: The sound gets quiet and stops. When the bell stops vibrating, it stops making sound.

Try It and Notice

1. Rubber band sound: Stretch a rubber band over a box with help from an adult. Pluck it gently. Watch and listen. The rubber band vibrates and makes sound.
2. Throat check: Put your fingers gently on your throat. Say your name. Feel the tiny vibrations.
3. Table tap: Tap a table softly. Listen to the sound. The table vibrates a little when you tap it.

Important Ideas to Remember

• All sound starts with vibration.
• Vibration means moving back and forth.
• Vibrating matter moves the air.
• The moving air carries sound to our ears.
• If the vibration stops, the sound stops.

Brief Summary

Sound is made when something vibrates. A vibration is a back-and-forth movement. The vibration moves the air, and that sound travels to our ears. Drums, bells, strings, and our voices all make sound because they vibrate.

Frequency and Pitch

We hear many sounds every day. A bird can chirp. A drum can boom. A whistle can squeak. Some sounds are high, and some sounds are low.

This lesson is about pitch. Pitch tells us if a sound is high or low.

Sounds are made when something vibrates. Vibrate means to move back and forth very fast. We may not always see the movement, but we can hear the sound it makes.

Think about a guitar string. When the string moves back and forth, it makes sound. Think about your throat when you talk. Your throat vibrates to make sounds too.

What is frequency?

Frequency means how fast something vibrates.

• If it vibrates fast, it makes a high-pitched sound.
• If it vibrates slowly, it makes a low-pitched sound.

You can think of it like this:

Fast vibration = high pitch

Slow vibration = low pitch

We can show that idea like this:

$$\text{fast vibrations} \rightarrow \text{high sound}$$

$$\text{slow vibrations} \rightarrow \text{low sound}$$

Main Idea

The speed of a vibration changes the pitch of a sound.

When vibrations happen many times very quickly, the sound is high. When vibrations happen fewer times and more slowly, the sound is low.

Examples in real life

• A small bell often makes a high sound.
• A big drum often makes a low sound.
• A bird chirp is often high.
• A lion roar is often low.

How your ears notice pitch

Your ears help your body hear sound. Your brain helps you tell if the sound is high or low.

When you hear a tiny squeak, you may say, “That is a high sound.” When you hear a deep boom, you may say, “That is a low sound.”

Worked Example 1

A bee is buzzing very fast. Is the sound more likely high or low?

Step 1: Listen to the clue: the bee is vibrating very fast.

Step 2: Fast vibrations make a high pitch.

Answer: The bee’s sound is more likely high.

Worked Example 2

A big drum makes slow vibrations. Is the sound high or low?

Step 1: The drum vibrations are slow.

Step 2: Slow vibrations make a low pitch.

Answer: The drum makes a low sound.

Worked Example 3

Which sound is higher: a little whistle or a big drum?

Step 1: A whistle usually vibrates faster.

Step 2: A drum usually vibrates more slowly.

Step 3: Faster vibrations mean higher pitch.

Answer: The little whistle has the higher sound.

Worked Example 4

Two sounds are playing. Sound A vibrates fast. Sound B vibrates slowly. Which sound has the lower pitch?

Step 1: Fast means high.

Step 2: Slow means low.

Answer: Sound B has the lower pitch.

Try to remember

• Pitch means how high or low a sound is.
• Vibrate means move back and forth.
• Frequency means how fast something vibrates.
• Fast vibrations make high sounds.
• Slow vibrations make low sounds.

Easy way to think about it

If a sound is a quick little squeak, it is probably high. If a sound is a big slow boom, it is probably low.

Brief Summary

Sound comes from vibrations. Pitch tells us if a sound is high or low. When something vibrates fast, it makes a high-pitched sound. When something vibrates slowly, it makes a low-pitched sound.

Amplitude and Volume

We hear sound with our ears. Sound happens when something vibrates, or moves back and forth very fast.

When a drum is hit, when hands clap, or when we talk, something is vibrating. Those vibrations make sound that travels to our ears.

Today we will learn about amplitude and volume.

Amplitude means how big a vibration is.

Volume means how loud or quiet a sound is.

Big vibrations make louder sounds. Small vibrations make quieter sounds.

So we can remember:

• Big amplitude = loud sound
• Small amplitude = quiet sound

If we use more force, the object can vibrate more. That makes a bigger amplitude.

If we use less force, the object vibrates less. That makes a smaller amplitude.

This means:

• More force → bigger amplitude → louder volume
• Less force → smaller amplitude → quieter volume

Think about pushing a swing. A small push makes a small move. A big push makes a big move. Sound vibrations can be small or big, too.

Let’s look at some everyday examples.

• If you tap a drum softly, it makes a quiet sound.
• If you hit a drum harder, it makes a loud sound.
• If you whisper, your voice is quiet.
• If you shout, your voice is loud.
• If you gently ring a bell, it sounds quiet.
• If you ring the bell with more force, it sounds louder.

Your ears can notice volume. They can tell if a sound is loud or quiet.

Let’s learn one important idea: loud does not mean better. Some sounds should be quiet. A lullaby is soft and gentle. A fire alarm is loud to help people notice it.

We can also compare sounds.

• A whisper is quieter than a shout.
• A soft drum tap is quieter than a hard drum hit.
• A gentle clap is quieter than a big clap.

Here is a simple way to think about it:

Small vibration: ~

Big vibration: ~~~~~

The bigger vibration makes the louder sound.

We can even put the idea in an arrow chain:

$$\text{more force} \rightarrow \text{bigger vibration} \rightarrow \text{louder sound}$$

And:

$$\text{less force} \rightarrow \text{smaller vibration} \rightarrow \text{quieter sound}$$

Now let’s work through some examples together.

Worked Example 1

Mia taps a drum very softly. Is the sound loud or quiet?

Step 1: She taps softly, so she uses less force.

Step 2: Less force makes a smaller vibration.

Step 3: Smaller vibration means quieter volume.

Answer: The sound is quiet.

Worked Example 2

Jay hits a drum hard. Is the amplitude small or big?

Step 1: Hitting hard means more force.

Step 2: More force makes a bigger vibration.

Answer: The amplitude is big.

Worked Example 3

Lina whispers to her friend. Then she calls across the playground. Which voice has bigger amplitude?

Step 1: A whisper is quiet.

Step 2: Calling across the playground is louder.

Step 3: Louder sound means bigger vibration.

Answer: Calling across the playground has bigger amplitude.

Worked Example 4

Two bells ring. Bell A is quiet. Bell B is loud. Which bell has the bigger amplitude?

Step 1: Quiet sound means smaller amplitude.

Step 2: Loud sound means bigger amplitude.

Answer: Bell B has the bigger amplitude.

Let’s practice thinking like scientists. Ask these questions:

1. What is making the sound?
2. Is it vibrating a little or a lot?
3. Does it sound quiet or loud?

If it vibrates a lot, the amplitude is bigger and the sound is louder.

If it vibrates only a little, the amplitude is smaller and the sound is quieter.

Things to remember

• Sound comes from vibrations.
• Amplitude tells how big the vibration is.
• Volume tells how loud or quiet the sound is.
• Big amplitude makes loud sounds.
• Small amplitude makes quiet sounds.

Brief Summary

Sound is made by vibrations. When vibrations are bigger, the amplitude is bigger and the volume is louder. When vibrations are smaller, the amplitude is smaller and the volume is quieter. We can notice this with drums, bells, claps, whispers, and shouts.

Thermal Conduction and Insulation

Have you ever touched a metal spoon in warm soup and felt that the spoon got warm too? Or put on a cozy blanket and felt warmer? That is because heat moves.

Heat is a kind of energy that makes things feel warm or hot. Heat likes to move from something warmer to something cooler.

This lesson will help you learn two big ideas:

• Conduction: when heat moves through things that are touching.
• Insulation: when a material slows down heat moving.

1. Heat moves from warm to cool

If one thing is hot and another thing is cooler, heat moves to the cooler thing. This keeps happening until the two things become more alike in temperature.

We can think about it like this:

Warm object \(\rightarrow\) cool object

For example, if you hold an ice cube in your hand, your hand is warmer than the ice cube. Heat moves from your hand to the ice cube, so the ice cube starts to melt.

2. What is conduction?

Conduction is when heat moves through materials that are touching. The heat travels from the warmer part to the cooler part.

If a pot of soup is hot, a spoon sitting in the soup can get warm. The spoon touches the soup, so heat moves into the spoon. That is conduction.

Conduction happens best when things are in contact, or touching.

3. Some materials let heat move fast

Some materials let heat travel through them quickly. These are called conductors.

Many metals are good conductors. A metal pan, a metal spoon, or a metal doorknob can feel hot or cold quickly because heat moves through metal well.

Examples of conductors:

• metal spoon
• metal pan
• aluminum foil

If you touch a metal slide on a sunny day, it may feel very hot. The heat moved through the metal easily.

4. Some materials slow heat down

Some materials do not let heat move quickly. These are called insulators.

Insulators slow down heat transfer. They help keep warm things warm and cool things cool for longer.

Examples of insulators:

• blankets
• oven mitts
• wood
• plastic
• foam

An oven mitt helps protect your hand from a hot pan because the mitt slows the heat moving to your hand.

A jacket helps keep your body warm because it slows heat from leaving your body.

5. Conductors and insulators in everyday life

We use conductors and insulators every day.

• A metal pot helps heat move from the stove to the food.
• A plastic handle on a pan helps keep your hand safer.
• A thermos helps drinks stay warm or cold longer.
• A blanket helps keep heat close to your body.

So, conductors can be useful when we want heat to move. Insulators can be useful when we want heat to move more slowly.

6. Warm, warmer, and cooler

Let us compare temperatures in a simple way:

• Hot means very warm.
• Warm means not too hot and not cold.
• Cool means less warm.
• Cold means very cool.

If a warm thing touches a cool thing, heat moves to the cool thing.

We can show this idea like this:

hot \(\rightarrow\) warm \(\rightarrow\) cool

Worked Example 1

Question: Mia puts a metal spoon into a bowl of hot oatmeal. After a little while, the spoon feels warm. Why?

Step 1: The oatmeal is hotter than the spoon.

Step 2: The spoon is touching the oatmeal.

Step 3: Heat moves from the hot oatmeal to the cooler spoon.

Answer: The spoon gets warm because of conduction.

Worked Example 2

Question: Ben uses an oven mitt to carry a warm tray. Why does he use the mitt?

Step 1: The tray is warm.

Step 2: Ben does not want too much heat to move to his hand.

Step 3: The oven mitt is an insulator.

Answer: Ben uses the mitt because it slows heat from moving to his hand.

Worked Example 3

Question: Which is better for stirring hot soup: a metal spoon or a wooden spoon if you want the handle to stay cooler?

Step 1: Metal is a good conductor.

Step 2: Wood is a better insulator.

Step 3: An insulator slows heat moving to the handle.

Answer: A wooden spoon is better if you want the handle to stay cooler.

Worked Example 4

Question: Lily wraps a cold juice box in a thick cloth. What will the cloth do?

Step 1: The room is warmer than the cold juice box.

Step 2: Heat wants to move from the warmer room to the cooler juice box.

Step 3: The cloth is an insulator, so it slows that heat transfer.

Answer: The cloth helps the juice box stay cold longer.

Things to remember

• Heat moves from warmer things to cooler things.
• Conduction happens when things touch and heat moves through them.
• Conductors let heat move quickly.
• Insulators slow heat down.

Quick check

1. If you touch a cold ice pop, does heat move from your hand to the ice pop, or from the ice pop to your hand?
2. Is a metal pan a conductor or an insulator?
3. Is a blanket used more like a conductor or an insulator?

Answers:

1. Heat moves from your hand to the ice pop.
2. A metal pan is a conductor.
3. A blanket is an insulator.

Summary

Heat moves from warmer objects to cooler objects. When heat moves through things that are touching, that is called conduction.

Materials like metal are conductors because heat moves through them quickly. Materials like cloth, wood, plastic, and oven mitts are insulators because they slow heat down.

Now you know why a metal spoon can get hot and why a blanket helps keep you warm!