Energy Forms, Transfer, and Conservation

The Nature of Energy

Energy is what makes things happen. It can make things move, glow, warm up, or make sounds. We cannot always see energy, but we can see what it does.

Think about a lamp. When you turn it on, it gives light. Think about a drum. When you tap it, it makes sound. Think about the Sun. It gives us light and warmth. These are all ways energy works in our world.

What is energy?

Energy is the ability to make a change. Energy can help something move. Energy can make something brighter, louder, or warmer. Energy helps many things on Earth work.

We notice energy by its effects

Energy can:

• make things move
• make things give light
• make things make sound
• make things feel warm or hot

If you kick a ball, energy makes the ball move. If you ring a bell, energy makes a sound. If you sit in the sunshine, energy from the Sun helps you feel warm.

Forms of energy we can observe

In first grade, we can learn about energy by looking at forms we can notice with our senses.

• Light energy helps us see. The Sun, a flashlight, and a lamp give light.
• Sound energy is what we hear. A drum, a dog bark, and clapping hands make sound.
• Thermal energy is heat. A warm cup of soup, a heater, and the Sun can make things warm.

Energy can travel

Energy can move from one place to another. Light travels from a lamp to your eyes. Sound travels from a bell to your ears. Heat travels from a warm object to your hands when you hold it carefully.

This is why energy is important. It goes through space and through materials to cause changes around us.

Energy and our senses

Our bodies can notice energy.

• We use our eyes to notice light.
• We use our ears to notice sound.
• We use our skin to notice warmth.

When energy reaches us, it helps us learn about the world.

Energy causes change

When energy is present, things can change. A toy car can start moving. Ice can begin to melt in warmth. A room can get brighter when a light turns on. A quiet space can become noisy when music starts.

So, when we ask, “What is energy?” we can say: Energy is what can cause change.

Examples from everyday life

• You flip on a flashlight. The room gets brighter. That is light energy.
• You hit a triangle in music class. You hear a ring. That is sound energy.
• You stand near a heater. You feel warmer. That is thermal energy.
• You push a swing. It starts moving. Energy helped cause motion.

Worked Example 1

Question: A lamp is turned on. What change happens?

Answer: The lamp gives off light, and the room gets brighter.

Why? Energy from the lamp causes a change we can see with our eyes.

Worked Example 2

Question: Ben claps his hands. What kind of energy do we notice?

Answer: We notice sound energy.

Why? Clapping makes sound, and our ears hear it.

Worked Example 3

Question: Mia sits in the sunshine and feels warm. What kind of energy is this?

Answer: This is thermal energy, or heat.

Why? The Sun gives energy that can warm things up.

Worked Example 4

Question: A room is dark and quiet. Then someone turns on a flashlight and rings a bell. What changes happen?

Answer: The room gets brighter, and a sound is heard.

Why? The flashlight gives light energy, and the bell gives sound energy. Energy caused two changes.

Let’s remember

• Energy makes things happen.
• Energy can cause change.
• We can notice energy as light, sound, and heat.
• Energy can travel from one place to another.
• Our eyes, ears, and skin help us notice energy.

Brief Summary

Energy is the ability to make changes in the world around us. We may not always see energy itself, but we can see and feel what it does. Light helps us see, sound helps us hear, and thermal energy helps us feel warmth. Energy is all around us every day.

Thermal and Electrical Conductivity

Everything around us is made of matter. Matter can be wood, metal, plastic, water, glass, cloth, and more.

Some kinds of matter let heat move through them easily. Some kinds of matter let electricity move through them easily.

When we learn about how heat and electricity move through materials, we are learning about conductivity.

Thermal conductivity means how well something lets heat travel through it.

Electrical conductivity means how well something lets electricity travel through it.

A material that lets heat or electricity move through easily is called a conductor.

A material that does not let heat or electricity move through easily is called an insulator.

We can sort materials into two big groups:

• Conductors — let heat or electricity pass through easily
• Insulators — slow down or stop heat or electricity

Part 1: Thermal Conductivity

Thermal is another word for heat.

Think about a metal spoon in a bowl of hot soup. After a little while, the spoon gets hot. That is because heat moved through the metal.

Metal is usually a good thermal conductor. It lets heat move quickly.

Now think about holding a hot pan with an oven mitt. The oven mitt helps protect your hand. That is because the mitt is a thermal insulator. It does not let heat move through easily.

Here are some common examples:

• Thermal conductors: metal spoon, metal pan, aluminum foil
• Thermal insulators: oven mitt, wood handle, cloth, plastic foam

Part 2: Electrical Conductivity

Electricity is the energy that can power lights, toys, and machines.

Some materials let electricity move through them. These materials are electrical conductors.

Metal is often a good electrical conductor too. That is why many wires are made of metal.

But you may notice that wires have plastic on the outside. The metal inside carries the electricity. The plastic outside helps keep us safe. Plastic is an electrical insulator.

Here are some common examples:

• Electrical conductors: copper wire, metal paper clip, aluminum
• Electrical insulators: rubber, plastic, wood, cloth

Important Safety Rule: Electricity can be dangerous. Only grown-ups should handle outlets, plugs, and wires.

How Are They the Same?

Thermal conductivity and electrical conductivity are alike because both tell us how well something lets something else move through it.

• Thermal conductivity = how well heat moves
• Electrical conductivity = how well electricity moves

Some materials, like many metals, are good at both.

How Are They Different?

They are different because one is about heat and the other is about electricity.

• A metal pot gets hot fast because metal conducts heat.
• A wire works because metal conducts electricity.

Why This Matters

Knowing if something is a conductor or an insulator helps us choose the right material for a job.

• We use metal pots because heat can move through them to cook food.
• We use wooden or plastic handles because they help protect our hands from heat.
• We use metal inside wires to carry electricity.
• We use rubber or plastic outside wires to help keep people safe.

Worked Example 1

Question: A spoon in hot cocoa gets hot after sitting in the cup. Is the spoon acting like a conductor or an insulator?

Think: Heat moved through the spoon and made it hot.

Answer: The spoon is acting like a conductor.

Why: A conductor lets heat move through it easily.

Worked Example 2

Question: A child uses a thick cloth potholder to carry a warm dish. Is the cloth a conductor or an insulator?

Think: The cloth helps stop the heat from reaching the hand quickly.

Answer: The cloth is an insulator.

Why: An insulator slows down heat.

Worked Example 3

Question: A wire has metal inside and plastic outside. Which part is the conductor, and which part is the insulator?

Think: The metal carries the electricity. The plastic helps keep hands safe.

Answer:

• The metal inside is the conductor.
• The plastic outside is the insulator.

Worked Example 4

Question: Look at these materials: metal, rubber, wood, and plastic. Which are most likely conductors, and which are most likely insulators?

Think: Metals often let heat and electricity move easily. Rubber, wood, and plastic usually do not.

Answer:

• Conductor: metal
• Insulators: rubber, wood, plastic

Quick Tips to Remember

• Conductor = lets heat or electricity go through
• Insulator = slows down or stops heat or electricity
• Metal is often a conductor
• Plastic, rubber, cloth, and wood are often insulators

Let’s Sort Some Objects

Here is one way to think about everyday objects:

• Metal spoon → usually a thermal conductor
• Oven mitt → usually a thermal insulator
• Copper wire → usually an electrical conductor
• Rubber band → usually an electrical insulator

Brief Summary

Materials can be grouped by how they let heat or electricity move.

If a material lets heat or electricity move through easily, it is a conductor.

If a material slows down or stops heat or electricity, it is an insulator.

Metals are often conductors. Plastic, rubber, wood, and cloth are often insulators.

Learning this helps us understand how to stay safe and how to choose the best materials for different jobs.

Refraction Fundamentals means that light can bend when it moves from one clear material to another clear material.

For example, light can travel through air, water, or glass. When light goes from air into water, it bends a little. This bending is called refraction.

We cannot usually see light bending by itself, but we can see what it does. It can make an object look like it moved, changed shape, or got a little bigger.

Introduction

Have you ever looked at a straw in a cup of water? The straw may look bent where it meets the water. The straw is not really broken. It only looks bent because the light changed direction.

This is an important idea in science: sometimes our eyes see something in a new way because of how light travels.

Main Teaching Points

1. Light travels

Light moves from place to place. It helps us see things around us.

Light can travel through some materials. Materials like air, water, and glass are clear, so light can go through them.

2. Light can bend

When light moves through the same kind of material, it keeps going along.

When light goes from one material to a different material, it can bend. For example:

• from air to water
• from water to air
• from air to glass

This bend is called refraction.

3. Refraction changes how things look

Because the light bends, the object we look at may seem different from where it really is.

Something in water might look:

• bent
• wiggly
• closer
• a little bigger

The object did not change. The light changed direction.

4. Refraction happens with clear materials

Refraction happens when light passes through transparent materials. Transparent means see-through.

Some transparent materials are:

• air
• water
• glass

If we cannot see through a material, it is harder for light to pass through it in the same way.

5. Our eyes notice the change

Our eyes and brain work together to help us see. When light bends before it reaches our eyes, what we see can look a little different.

That is why a fish in water may seem to be in a slightly different place than it really is.

Examples

Example 1: A straw in water

You put a straw into a clear cup of water.

What do you see? The straw may look bent at the top of the water.

Why? Light from the part of the straw under the water bends as it comes into the air. Your eyes see that bent light, so the straw looks bent.

Example 2: A coin in a cup

Put a coin in an empty cup. Look at it. Then carefully add water.

The coin may look like it moved or became easier to see.

Why? The light from the coin bends when it moves from water into air. This can change how the coin looks to your eyes.

Example 3: A fish in water

Look at a fish in a tank or pond.

The fish may look a little closer or in a different spot.

Why? Light from the fish travels through water, then through air, and bends along the way. That makes the fish seem to be in a new place.

Worked Examples

Worked Example 1

Question: A spoon is in a glass of water. It looks bent. Is the spoon really bent?

Answer: No. The spoon is not really bent.

Step by step:

1. The spoon is partly in air and partly in water.
2. Light travels from the spoon through the water and into the air.
3. The light bends.
4. Your eyes see the spoon as bent.

Conclusion: The spoon only looks bent because of refraction.

Worked Example 2

Question: Mia looks at a toy at the bottom of a clear tub of water. The toy looks a little bigger. Did the toy grow?

Answer: No. The toy did not grow.

Step by step:

1. The toy stays the same size.
2. Light from the toy moves through water and then air.
3. The light bends.
4. Mia’s eyes see the toy differently.

Conclusion: Refraction can make the toy look different, even though it stayed the same.

Worked Example 3

Question: Ben puts a pencil into a cup of water. Which part of the path has bending: only in air, or where air and water meet?

Answer: The bending happens where air and water meet.

Step by step:

1. Light travels through air.
2. Light travels through water.
3. When light moves from one clear material to the other, it bends.

Conclusion: Refraction happens when light goes from one transparent material to another.

Try to Notice It

• Look at a straw or spoon in water.
• Look at pebbles under clear water.
• Look through a glass of water at a picture behind it.

Each time, ask: Does the object look different because light is bending?

Important Ideas to Remember

• Light helps us see.
• Light can travel through clear materials.
• Light bends when it moves from one clear material to another.
• This bending is called refraction.
• Refraction can make objects look bent, moved, or different.

Brief Summary

Refraction is when light bends as it moves from one transparent material to another, like from air to water.

Because the light bends, objects can look bent, bigger, or in a different place. The object does not really change. The light changes direction.

Acoustic Transmission Media means what sound travels through.

Sound can travel through solids, liquids, and gases. These are all kinds of matter.

Matter is the stuff things are made of. A table is matter. Water is matter. Air is matter.

Sound needs matter to move. Sound cannot travel where there is no matter.

When something makes a sound, it vibrates. Vibrate means to move back and forth very fast.

Those vibrations move through matter and travel to our ears. Then we hear the sound.

Introduction

Have you ever heard a friend knock on a door? Have you heard splashing in water? Have you heard a bird singing in the air?

All of these sounds travel, but they do not all travel the same way. Some kinds of matter help sound move better than others.

In this lesson, we will learn that sound travels best through solids, next through liquids, and slowest through gases.

Main Teaching Points

1. Sound is made by vibrations.

A drum makes sound when its top shakes. A bell makes sound when it rings and shakes. Your voice makes sound when part of your throat vibrates.

If nothing vibrates, no sound is made.

2. Sound needs something to travel through.

Sound cannot move by itself. It must move through some kind of matter.

• Solid: desk, wall, spoon, floor
• Liquid: water, juice, milk
• Gas: air

We hear many sounds through the air, so air is a very important medium for sound. But air is not the best one.

3. Sound travels best through solids.

In a solid, the tiny parts are packed close together. This helps the vibration move quickly from one part to the next.

That is why you may hear a knock better by touching your ear to a door or a table.

4. Sound also travels through liquids.

Sound can move through water. If you splash, tap, or kick in water, sound can travel there too.

Sound moves through liquids, but not as well as through solids.

5. Sound travels slowest through gases.

Air is a gas. We hear through air every day, but sound moves slower in air than in solids or liquids.

This is because the tiny parts in a gas are farther apart.

Think of it like this:

1. Best: solids
2. Next: liquids
3. Slowest: gases

Easy order to remember:

solid → liquid → gas

Examples from everyday life

• You hear footsteps through the floor. The floor is a solid.
• You hear splashing underwater. Water is a liquid.
• You hear someone talking across the room. Air is a gas.

Worked Example 1

Question: A child taps a desk. What does the sound travel through?

Step 1: Think about what the desk is made of.

The desk is hard. It is a solid.

Step 2: Sound can travel through solids.

Answer: The sound travels through a solid.

Worked Example 2

Question: You hear a splash in a pool. What medium is helping the sound travel?

Step 1: A pool is filled with water.

Step 2: Water is a liquid.

Answer: The sound is traveling through a liquid.

Worked Example 3

Question: Your teacher talks, and you hear the voice across the classroom. What medium is the sound traveling through?

Step 1: The classroom is filled with air.

Step 2: Air is a gas.

Answer: The sound is traveling through a gas.

Worked Example 4

Question: Which helps sound travel best: a wall, water, or air?

Step 1: Name each kind of matter.

• Wall = solid
• Water = liquid
• Air = gas

Step 2: Remember the order: solid, liquid, gas.

Answer: The wall helps sound travel best because it is a solid.

Helpful Check

If you are not sure, ask:

• Is it hard and keeps its shape? It is probably a solid.
• Does it pour and splash? It is probably a liquid.
• Is it the air around us? It is a gas.

What students should remember

• Sound is made by vibrations.
• Sound needs matter to travel.
• Sound can travel through solids, liquids, and gases.
• Sound travels best through solids.
• Sound travels through liquids next.
• Sound travels slowest through gases.

Brief Summary

Sound is made when something vibrates. The sound moves through matter to reach our ears.

Sound can travel through solids, liquids, and gases. It travels best through solids, less well through liquids, and slowest through gases like air.

Kinetic and Potential Energy

Energy is what helps things happen. Energy can make things move, change, or work.

Today we will learn about two kinds of energy: kinetic energy and potential energy.

Kinetic energy is the energy of motion. If something is moving, it has kinetic energy.

Potential energy is stored energy. It is energy that is ready to be used.

We can think about it like this:

• Kinetic = moving
• Potential = stored

Introduction to Kinetic Energy

When you run, your body is moving. That means you have kinetic energy.

When a ball rolls across the floor, it is moving. A rolling ball has kinetic energy.

A car driving on the road, a bird flying in the sky, and a skateboard zooming down the sidewalk all have kinetic energy because they are in motion.

If something is not moving, it does not have kinetic energy right then.

Introduction to Potential Energy

Potential energy is energy that is saved up or stored.

Think about a rock sitting at the top of a hill. It is not moving yet, so it does not have kinetic energy. But it has potential energy because it could roll down the hill.

Think about a swing pulled back before it starts moving. The swing has stored energy. That is potential energy.

Food also stores energy. Your body uses the stored energy in food to run, jump, and play. That is another kind of potential energy.

How They Work Together

Kinetic energy and potential energy can change from one to the other.

Imagine a ball at the top of a slide. At the top, it has potential energy because it is high up and ready to move.

When the ball starts to roll down, its stored energy changes into kinetic energy. Now the ball is moving.

At the bottom, the ball has less stored energy from being high up, but it has kinetic energy because it is still moving.

This means energy can change form:

• Stored energy can become moving energy.
• Moving energy can become stored energy.

Examples Around Us

• A child sitting still at the top of a slide has potential energy.
• The child sliding down has kinetic energy.
• A stretched rubber band has potential energy.
• A rubber band flying through the air has kinetic energy.
• A book resting on a high shelf has potential energy.
• A book falling off the shelf has kinetic energy.

Easy Clue Words

You can ask yourself these questions:

• Is it moving? If yes, it has kinetic energy.
• Is it stored, waiting, or up high? If yes, it may have potential energy.

Worked Example 1

Question: A soccer ball is rolling across the grass. Is that kinetic energy or potential energy?

Step 1: Ask, “Is it moving?”

Step 2: Yes, the ball is rolling.

Answer: The ball has kinetic energy because it is moving.

Worked Example 2

Question: A toy car is sitting still at the top of a ramp. Is that kinetic energy or potential energy?

Step 1: Ask, “Is it moving?”

Step 2: No, it is sitting still.

Step 3: Ask, “Is the energy stored and ready to move?”

Step 4: Yes, it is at the top of the ramp and could roll down.

Answer: The toy car has potential energy.

Worked Example 3

Question: A child climbs up a ladder and then slides down a slide. What kind of energy does the child have at the top? What kind of energy does the child have while sliding?

Step 1: At the top, the child is high up and waiting to move.

Step 2: That means the child has potential energy.

Step 3: While sliding, the child is moving.

Step 4: That means the child has kinetic energy.

Answer: At the top: potential energy. While sliding: kinetic energy.

Worked Example 4

Question: A rubber band is pulled back and then let go. What kind of energy does it have before it is let go? What kind after it snaps forward?

Step 1: Before it is let go, the rubber band is stretched and not moving.

Step 2: It has stored energy, so that is potential energy.

Step 3: After it is let go, it moves fast.

Step 4: Moving means kinetic energy.

Answer: Before: potential energy. After: kinetic energy.

Try to Remember

• Kinetic energy means energy of motion.
• Potential energy means stored energy.
• Things can change from potential energy to kinetic energy.
• Things can also change from kinetic energy to potential energy.

Mini Check

1. A bike riding down the street has kinetic energy.
2. An apple hanging on a tree has potential energy.
3. A basketball flying through the air has kinetic energy.
4. A sled waiting at the top of a snowy hill has potential energy.

Brief Summary

Energy helps things move and work. Kinetic energy is the energy of something that is moving. Potential energy is stored energy that is ready to be used.

When something starts to move, potential energy can change into kinetic energy. When you look at an object, ask: Is it moving, or is it stored and waiting? That will help you tell the difference.

Thermal energy is heat. Heat is what makes something feel warm or hot.

We can feel thermal energy when the sun warms our skin, when soup is hot, or when our hands get warm. In this lesson, we will learn that heat can be made in different ways.

There are three important ways we will learn about:

• Friction — rubbing things together
• Burning — a fire making heat
• Electricity — some things get warm when electricity moves through them

Let’s learn about each one.

1. Heat from friction

Friction happens when two things rub together. When they rub, they can make heat.

Try this: rub your hands together fast. After a little bit, your hands feel warmer. That warmth is thermal energy.

Friction can make heat in many places:

• rubbing hands together
• sliding on a playground pole
• bike tires touching the road

When things move and rub, they can get warm.

2. Heat from burning

Burning can also make heat. A campfire, a candle, or a stove flame gives off heat.

When something burns, it makes both heat and often light. That is why a fire looks bright and also feels hot.

Examples of burning that make heat:

• a campfire
• a candle flame
• a gas stove

Fire can be very hot, so we must stay safe around it. A grown-up should always help with fire.

3. Heat from electricity

Some things get warm when electricity moves through them. This can make thermal energy.

Think about a toaster, a hair dryer, or a space heater. These tools use electricity and can make heat.

Examples of electrical things that make heat:

• toaster
• heater
• clothes iron

These things can get very hot. We should only use them with adult help.

How can we tell heat is being made?

We may notice:

• something feels warm or hot
• steam rising from food or water
• we move our hands away because it is too hot

Sometimes we can feel the heat. Sometimes we can see clues, like steam or a glowing toaster.

Worked Example 1

Situation: Mia rubs her hands together on a cold day.

Question: What is making her hands warmer?

Answer: Friction is making heat.

Why? Her hands are rubbing together. Rubbing creates friction, and friction makes thermal energy.

Worked Example 2

Situation: A family sits near a campfire.

Question: Why do they feel warm?

Answer: The fire is making heat.

Why? Burning wood gives off thermal energy, so the people near the fire can feel the warmth.

Worked Example 3

Situation: Bread goes into a toaster and comes out warm and toasty.

Question: What is making the heat?

Answer: Electricity is making heat in the toaster.

Why? The toaster uses electricity to get hot. That heat warms the bread.

Worked Example 4

Situation: Ben slides down a metal slide. At the bottom, his clothes and the slide feel a little warmer.

Question: What made the warmth?

Answer: Friction made the warmth.

Why? Ben and the slide rubbed against each other while he moved. Rubbing can make heat.

Let’s compare the three ways heat can be made:

• Friction: rubbing things together makes heat
• Burning: fire makes heat
• Electricity: some machines use electricity to make heat

Safety reminders

• Do not touch fire.
• Do not touch hot stoves, toasters, or irons.
• Ask a grown-up for help with anything hot.

Summary

Thermal energy is heat. Heat can be made by friction, by burning, and by electricity.

We can feel heat when we rub our hands together, stand near a fire, or use something like a toaster. Knowing how heat is made helps us understand the world and stay safe.

Sound Energy is energy we can hear. When something vibrates, it moves back and forth very quickly. These vibrations make sound.

When you tap a drum, pluck a guitar string, or clap your hands, you make something vibrate. Those vibrations move through the air and travel to your ears. Then your brain helps you hear the sound.

Sound is a kind of energy because it can move from one place to another. Sound can travel through air, water, and solids like wood or metal.

Introduction: How does sound begin?

Sound begins when an object vibrates. A bell rings because the bell shakes. A speaker makes music because parts inside it vibrate. Even your voice is made when parts in your throat vibrate.

If nothing vibrates, no sound is made. Vibrations are the start of sound energy.

Main Teaching Point 1: Sound needs something to travel through

Sound does not move all by itself. It needs a medium. A medium is something sound can travel through, like:

• air
• water
• solids such as a desk, wall, or string

When sound travels, it pushes tiny bits of the medium forward and backward. This makes a longitudinal wave. That means the tiny bits move back and forth in the same direction the sound is traveling.

You do not need to memorize that big name. Just remember this: sound is a push-and-pull wave that moves through matter.

Imagine a line of children standing shoulder to shoulder. If one child gently leans forward and bumps the next, the push travels down the line. Sound works in a similar way. The push moves, even though each child only moves a little.

Main Teaching Point 2: Sound can travel through different materials

Sound can move through:

1. Air — This is how we hear talking, singing, and birds chirping.
2. Water — Sounds can travel in water too.
3. Solids — Sound can travel through a table, wall, floor, or string.

Have you ever put your ear on a desk and heard tapping more clearly? That is because sound can travel through the solid desk.

Main Teaching Point 3: Fast vibrations and slow vibrations

Some sounds are high, like a whistle. Some sounds are low, like a big drum. This is called pitch.

Pitch tells us if a sound is high or low.

• Fast vibrations make a high pitch.
• Slow vibrations make a low pitch.

The number of vibrations in a short time is called frequency. For 2nd grade, you can think of frequency as how fast something vibrates.

So remember:

• Higher frequency = higher pitch
• Lower frequency = lower pitch

A small bell may make a higher sound. A big drum may make a lower sound. That is because they can vibrate in different ways.

Main Teaching Point 4: Loud and soft sounds

Sound can also be loud or soft.

• A loud sound has bigger vibrations.
• A soft sound has smaller vibrations.

Pitch and loudness are not the same thing. A sound can be high and soft, like a tiny bird chirp. A sound can be low and loud, like thunder or a bass drum.

Worked Example 1: What made the sound?

Question: Maya hits a drum. What made the sound?

Step 1: Think about what starts sound. Sound starts with vibrations.

Step 2: When Maya hits the drum, the drum surface shakes back and forth.

Answer: The sound was made because the drum vibrated.

Worked Example 2: What does sound travel through?

Question: Leo taps on one end of a table. Ava puts her ear near the other end and hears it. What did the sound travel through?

Step 1: Find the material between the tap and Ava's ear.

Step 2: The table is a solid.

Answer: The sound traveled through the solid table.

Worked Example 3: Which sound has a higher pitch?

Question: One sound comes from fast vibrations. Another sound comes from slow vibrations. Which sound has the higher pitch?

Step 1: Remember the rule: fast vibrations make a high pitch.

Step 2: Compare the two sounds.

Answer: The sound with fast vibrations has the higher pitch.

Worked Example 4: Pitch or loudness?

Question: A whistle makes a high sound, but it is not very loud. What word tells about how high the sound is?

Step 1: Ask: Are we talking about high or low? Or loud or soft?

Step 2: High or low means pitch.

Answer: The word is pitch.

Examples from everyday life

• A guitar string vibrates when plucked, making sound.
• Your voice makes sound when parts in your throat vibrate.
• A train on a track can sometimes be heard through the rail because sound can travel through solids.
• A tiny bell often makes a higher pitch than a large drum.

Try to Remember

• Sound energy begins with vibrations.
• Sound travels through air, water, and solids.
• Sound is a longitudinal wave, a push-and-pull wave.
• Fast vibrations make high pitch.
• Slow vibrations make low pitch.
• Loud and soft are different from high and low.

Brief Summary

Sound energy is made when something vibrates. The vibrations travel through air, water, or solids to your ears. Sound travels as a push-and-pull wave called a longitudinal wave. Fast vibrations make a high pitch, and slow vibrations make a low pitch.