A unit of the course: the story, then chapter by chapter — sections, numbered lessons, a source or the numbers to read, three checks each — a review per chapter, and the wrap-up at the end.
Drawn scene: a bedroom at night where a flashlight throws a rabbit shadow puppet on the wall, with a drum on the floor and ripples in a glass of water
2Unit
Light, Sound and Waves
Physical Science
Tap a drum. Feel the buzz under your hand. Hear the boom. Turn off the lamp. The room goes dark. Your shadow is gone. Sound and light are all around you, every day. This unit is about both of them.
You will find out what a sound really is. It is a wiggle. Something shakes, and the shake spreads to your ear. You will find out what light does. It shines from the sun or a bulb. It bounces off things and into your eyes.
By the end, you can explain a drum. Why does it stop when you touch it? You can explain a shadow. Why does it move? And you can send a secret message. Use claps, or blinks of a flashlight.
How we figured it out
Wake up
An alarm buzzes. Something inside it is shaking fast. That shake is the sound.
Sunrise
Light comes in the window. Now you can see your room. The sun is a light source.
Breakfast
A spoon clinks on a bowl. The bowl vibrates. The sound spreads through the air.
Bus stop
Your shadow is long on the sidewalk. The sun is low in the sky.
Class
Hand on the drum machine. Feel the buzz. Loud hits make big wiggles.
Recess
A whistle blows. Everyone stops. The sound carried a message.
Noon
Shadows are very short now. The sun is high overhead.
Afternoon
You look through a window. Glass lets light through. The wall does not.
Dinner
A ship horn sounds on the lake in the fog. The horn says: I am here.
Dusk
The lighthouse beam turns on. Its light tells boats where the shore is.
Bedtime
You blink a flashlight to your sister. Two blinks mean no, one means yes.
Night
Lights off. The room is dark. You cannot see, but you can still hear.
3
Chapter
Sound Is a Wiggle
Waves
Big questionWhat is a sound, and how does it get from a drum to your ear?
The story
Hand on the Drum
You can feel a sound before you can name it.
Mia stands at the drum machine. The big drum is quiet. She puts her hand flat on the drum skin. It feels smooth and still. Nothing is moving. Then her teacher taps the drum once with a stick.
Boom! Mia feels a buzz under her hand. The skin shakes very fast. It tickles her palm. The buzz gets smaller and smaller. Then it stops. The sound stops at the same time. Mia looks at her hand. It is not hurt. It just felt the drum wiggle.
She tries it again. This time she hits the drum herself. She hits it soft. The buzz is small. The sound is soft. She hits it hard. The buzz is big. The sound is loud. Mia grins. The drum wiggles, and that wiggle is the sound.
Now Mia puts her hand on her own throat. She hums. Her throat buzzes too, just like the drum. She stops humming. The buzz stops. Mia has found a rule. Where there is a sound, something is wiggling.
Talk about itMia felt the drum buzz and heard the sound at the same time. Why do you think the buzz and the sound stopped together?
Section 1
Things That Wiggle
3.1
The Drum Skin Shakes
Main ideaA sound comes from something that shakes back and forth very fast.
Tap a drum. The skin moves. It goes up and down very fast. This fast shaking is called a . You can feel it with your hand. You can hear it with your ear.
The shaking makes the sound. When the skin stops shaking, the sound stops. No shaking means no sound. Try it. Tap the drum. Then press your hand on it. The sound dies fast.
Words to know
vibration
a very fast shaking back and forth
Check yourself
1. What is a vibration?
Why: A vibration is a fast shaking back and forth. The drum skin vibrates when you tap it.
2. You press your hand on a ringing drum. What happens?
Why: Your hand stops the skin from shaking. No shaking means no sound.
3. What makes the drum's sound?
Why: The shaking skin makes the sound. The stick just starts the shaking.
3.2
Rubber Bands and Throats
Main ideaMany things vibrate to make sound, even your own throat.
Stretch a rubber band. Pluck it. It looks blurry for a second. It is shaking too fast to see. You hear a twang. Pinch the band. It stops. The twang stops too.
Put your hand on your throat. Say your name. Feel the buzz? Two small flaps in your throat shake. They make your voice. Whisper your name. The buzz is gone. Whispers do not use the flaps.
Words to know
pluck
to pull a string and let it go so it shakes
Check yourself
1. You pluck a rubber band. Why does it look blurry?
Why: The band moves back and forth so fast that your eyes see a blur.
2. When can you feel a buzz in your throat?
Why: Humming makes the flaps in your throat shake. Whispers do not shake them.
3. What happens if you pinch a twanging rubber band?
Why: Pinching stops the shaking. When the shaking stops, the sound stops.
Section 2
Loud, Soft, High, Low
3.3
Sound Moves Things
Main ideaSound can make other things vibrate too, like rice on a drum.
Put a few grains of rice on a drum. Do not touch the drum. Stand near it. Clap hard, or bang a pot. Watch the rice. It jumps! Your sound made the drum skin shake.
Sound is a wiggle that spreads out. It goes through the air. It reaches the drum. The skin wiggles a tiny bit. The rice hops. Sound can move things without a touch.
Words to know
spread
to move out in every direction from one spot
Check yourself
1. Rice jumps on a drum when you clap. Why?
Why: The sound of the clap spread through the air. It made the skin vibrate, so the rice hopped.
2. The boy bangs the pot very hard. What does the rice do?
Why: A bigger sound makes a bigger wiggle in the drum. The rice hops more.
3. How does the clap sound get to the drum?
Why: The sound spreads out through the air and reaches the drum.
3.4
Loud and Soft
Main ideaA big wiggle makes a loud sound; a small wiggle makes a soft sound.
Tap a drum softly. The skin moves a little. The sound is soft. Hit it hard. The skin moves a lot. The sound is . A bigger wiggle makes a louder sound.
Loud sounds can hurt your ears. Fire trucks and lawn mowers are very loud. Cover your ears near them. A whisper is very soft. You must be close to hear it.
Sounds get softer as they spread out. A friend yells from across the field. It sounds soft. The same yell up close is loud. The wiggle gets weaker the farther it goes.
Words to know
loud
a sound that is big and strong, easy to hear
Check yourself
1. How do you make a drum louder?
Why: A harder hit makes a bigger wiggle. A bigger wiggle is a louder sound.
2. Which sound is the softest?
Why: A whisper is a very small wiggle. You must be close to hear it.
3. A friend yells from far away. How does it sound?
Why: Sound gets weaker as it spreads out. Far away, the yell sounds soft.
3.5
High and Low
Main ideaFast wiggles make high sounds; slow wiggles make low sounds.
A bird’s chirp is . A big dog’s bark is . High and low is not about loud and soft. A high sound can be soft. A low sound can be loud.
Stretch a rubber band tight. Pluck it. The sound is high. Let it go loose. Pluck it. The sound is low. A tight band shakes faster. Faster shaking makes a higher sound.
Big things often make low sounds. A big drum goes boom. A tiny drum goes tap. Small things wiggle faster. Try tapping a big pot and a small cup.
Words to know
high
a sound like a bird chirp or a whistle
low
a sound like a big drum or a big dog's bark
Check yourself
1. Which sound is high?
Why: A bird chirp is a fast wiggle, so it sounds high.
2. A rubber band is stretched tight. Its sound is:
Why: A tight band shakes faster. Faster shaking makes a higher sound.
3. Is a high sound always loud?
Why: High and low is about how fast the wiggle is. Loud and soft is about how big it is.
Section 3
Sound Travels
3.6
Through Air, Water and Wood
Main ideaSound can travel through air, through water and through solid things.
Sound needs something to move through. Air works. Water works. Wood works. Put your ear on a table. Have a friend tap the far end. You hear it clearly. The tap went through the wood.
Dip your ears under bath water. Tap the tub. You still hear it. Sound goes through water. Whales hear each other far away in the ocean this way.
Long ago, a scientist put a ringing bell in a jar. He pumped the air out. The ring got quiet. No air, no sound. Sound needs something to wiggle.
Words to know
travel
to move from one place to another
Check yourself
1. Your ear is on a table. A friend taps the other end. How did the sound reach you?
Why: Sound travels through solid things like wood. The tap moved through the table.
2. Can sound travel through water?
Why: Sound goes through water. Whales hear each other far away in the ocean.
3. The air was pumped out of the jar. What happened to the bell's ring?
Why: With no air in the jar, there was nothing to carry the wiggle out. The ring almost vanished.
3.7
The String Telephone
Main ideaA tight string can carry a voice from one cup to another.
Take two paper cups and a long string. Poke a hole in each cup. Tie the string to both. Pull it tight. Talk into one cup. Your friend puts the other cup to an ear.
Your voice shakes the cup. The cup shakes the string. The string shakes the other cup. Your friend hears you! Let the string go loose. Now it does not work. The wiggle needs a tight string.
Words to know
tight
pulled straight with no sag or slack
Check yourself
1. What carries the voice between the cups?
Why: The tight string carries the wiggle from one cup to the other.
2. The string goes loose. What happens?
Why: A loose string cannot carry the wiggle. The voice does not get through.
3. What must you do to the string first?
Why: The string must be tight so the wiggle can travel along it.
3.8
Sending a Message
Main ideaPeople use sounds like bells and whistles to send messages far away.
A sound can carry a message. A school bell says, come in. A whistle at recess says, stop and look. A fire alarm says, get out now. You do not need words.
Long ago, church bells told a whole town the time. Ships blow horns in fog so they do not crash. Sounds can travel farther than your voice.
You can make your own sound code. One clap means yes. Two claps mean no. Try it with a friend across the room.
Words to know
message
information sent from one person to another
Check yourself
1. What does a fire alarm tell you?
Why: A fire alarm is a sound message. It means leave the building right away.
2. Why do ships blow horns in fog?
Why: In fog, ships cannot see each other. The horn sound tells them where a ship is.
3. Two claps mean no. Your friend claps twice. What did they say?
Why: In the code, two claps mean no. Sounds can carry messages without words.
Chapter review
Sound Is a Wiggle
0 / 6
1. What is a sound?
Why: Sound comes from something shaking fast. The wiggle spreads out to your ear.
2. You hum and put a hand on your throat. What do you feel?
Why: Flaps in your throat vibrate when you hum. You feel that buzz.
3. Rice on a drum hops when you bang a pot. Why?
Why: The sound traveled through the air and shook the drum skin. The rice hopped.
4. Which wiggle makes a loud sound?
Why: A bigger wiggle makes a louder sound. A harder hit makes a bigger wiggle.
5. A tight rubber band and a loose one. Which sounds higher?
Why: The tight band shakes faster. Faster shaking makes a higher sound.
6. The string telephone needs the string to be:
Why: A tight string carries the wiggle from cup to cup. A loose one does not.
Send it to your teacher
4
Chapter
Light and Seeing
Waves
Big questionWhy can you see some things and not others, and where does light come from?
The story
Behind the Bedsheet
A lamp, a sheet and two hands can make a whole show.
Leo and his sister hang a white bedsheet across the doorway. Behind it, they set a lamp on the floor. Grandma sits on the other side. The lights in the room go off. The sheet glows soft and white.
Leo puts his hands between the lamp and the sheet. On Grandma's side, a dark dog appears! Its ears wiggle. It opens its mouth. Grandma laughs. Leo's hands block the light. Where the light cannot go, the sheet stays dark.
His sister moves her hand close to the lamp. Her rabbit shadow grows huge. She moves it near the sheet. The rabbit shrinks and gets sharp. Then Leo turns the lamp off. Everything is black. No lamp, no shadows, no show.
Leo turns the lamp back on. He holds up a glass of water. The sheet shows a fuzzy, bright shape, not a dark one. Light goes through the glass. Leo thinks: light goes through some things and is stopped by others.
Talk about itThe rabbit shadow got bigger when the hand moved closer to the lamp. Why do you think that happened?
Section 1
Light Lets Us See
4.1
The Dark Room
Main ideaYou need light to see anything; in a truly dark room you see nothing.
Go into a closet. Shut the door. Wait. Can you see your hand? If no light gets in, you cannot. Your eyes need to see. No light means no seeing.
Open the door a crack. A little light comes in. Now you see shapes. Open it wide. Now you see colors too. More light lets you see more.
Words to know
light
what lets your eyes see; it comes from the sun, fire and bulbs
Check yourself
1. What do your eyes need to see?
Why: Eyes only work when light reaches them. In a truly dark room you see nothing.
2. The closet door opens a crack. What do you see first?
Why: A little light shows shapes. You need more light to see colors well.
3. A red ball is in a totally dark room. What color does it look?
Why: With no light, nothing can be seen, not even a bright red ball.
4.2
Where Light Comes From
Main ideaThe sun, fire, and light bulbs make light; most things only bounce it.
Some things make their own light. The sun does. A candle flame does. A light bulb does. Each one is a light . It shines.
Most things do not shine. A book does not. Your hand does not. You see them because light from a source hits them and bounces to your eyes. The moon does not shine on its own. Sunlight bounces off it.
The sun is our biggest light source. It lights the whole day. At night we use bulbs, flashlights and fires.
Words to know
source
a thing that makes its own light, like the sun or a bulb
Check yourself
1. Which one makes its own light?
Why: A flame is a light source. A book and a rock only bounce light.
2. Why can you see a book?
Why: A book does not make light. Light from a source hits it and bounces into your eyes.
3. Does the moon make its own light?
Why: The moon is a big rock. We see it because the sun's light bounces off it.
Section 2
Through, Blocked, Shadow
4.3
Light Goes Through Glass
Main ideaSome materials let light through, some let a little through, and some block it.
Hold a window glass up to a lamp. You see the lamp clearly. Glass lets light through. Now hold up wax paper. You see a glow, but no clear lamp. Wax paper lets a little light through.
Now hold up a wood board. You see nothing. Wood can light. Try more things: a plastic bag, a leaf, a shirt, a cup. Sort them into three groups: all, a little, none.
Words to know
block
to stop light so it cannot go through
Check yourself
1. Which lets light through best?
Why: Clear glass lets almost all light through. You see the lamp clearly.
2. You hold wax paper up to a lamp. What do you see?
Why: Wax paper lets some light through, but it scatters it. You see a glow, not a clear shape.
3. What does a wood board do to light?
Why: Wood blocks light. No light gets through, so you see nothing behind it.
4.4
Shadows
Main ideaA shadow is the dark spot where something has blocked the light.
Stand in the sun. Look down. A dark shape is on the ground. It is your . Your body blocks the sunlight. The ground behind you stays dark.
Shadows change. Move close to a lamp. Your shadow grows big. Move away. It shrinks. Turn off the lamp. The shadow is gone. No light means no shadow.
In the morning, the sun is low. Shadows are long. At noon, the sun is high. Shadows are short. Chalk your shadow at recess. Check it after lunch.
Words to know
shadow
a dark spot made when something blocks light
Check yourself
1. What makes a shadow?
Why: A shadow is the dark place where light is blocked.
2. You turn off the only lamp. What happens to your shadow?
Why: No light means no shadow. A shadow is only a spot with light blocked.
3. When are shadows the shortest?
Why: At noon the sun is high in the sky. A high sun makes short shadows.
Section 3
Bouncing and Sending
4.5
Mirrors Bounce Light
Main ideaA mirror bounces light back so you can see yourself or send a beam.
A is very smooth and shiny. Light hits it and bounces straight back. That is why you see your face in it. The light from your face bounces to your eyes.
Shine a flashlight at a mirror. Tilt the mirror. The bright spot moves on the wall. You can aim light with a mirror. Kids can bounce a sun spot onto the ceiling.
Still water can act like a mirror. Look in a puddle. You see the sky. Wind makes ripples. Now the sky looks broken up.
Words to know
mirror
a smooth shiny surface that bounces light back
Check yourself
1. What does a mirror do to light?
Why: A mirror is smooth and shiny. Light bounces off it instead of going through.
2. You tilt a mirror in a sunbeam. What happens to the bright spot?
Why: Tilting the mirror changes where the light bounces. The spot moves.
3. Why does a puddle show the sky?
Why: Smooth, still water bounces light back like a mirror. Ripples break the picture up.
4.6
Blink a Message
Main ideaLight can carry a message, like a flashlight blink or a lighthouse beam.
You can talk with light. Make a code. One blink means yes. Two blinks mean no. Blink a flashlight to a friend across a dark yard. They blink back. No sound needed.
A is a tall tower with a big light. Its beam turns at night. Ships see it far out on the water. The light says: land is here, stay away from the rocks. Chicago has a lighthouse at its harbor on Lake Michigan.
Traffic lights send messages too. Red says stop. Green says go. You read the light before you cross.
Words to know
lighthouse
a tall tower with a bright light that warns ships
Check yourself
1. What does a lighthouse tell ships?
Why: The lighthouse beam warns ships that the shore and rocks are near.
2. Two blinks mean no. The flashlight blinks twice. The message is:
Why: In the code, two blinks mean no. Light can carry a message just like sound can.
3. Which light sends the message 'stop'?
Why: A red traffic light means stop. Green means go.
4.7
The Telescope Collects Light
Main ideaA telescope gathers lots of light so we can see faint, far things like the moon.
Stars are far away. Their light is faint. Your eye is small. It only catches a little light. A has a big lens or mirror. It catches much more light.
Look at the moon through a telescope. It looks bigger and brighter. You see bumps and holes. Those holes are craters. Long ago, Galileo did this. He was surprised the moon was not smooth.
The telescope on this site does the same job. It collects light. Then it sends it to your eye or a camera.
Words to know
telescope
a tool that collects light to show far-away things bigger
Check yourself
1. What does a telescope do with light?
Why: A telescope has a big lens or mirror that gathers more light than your eye can.
2. Through a telescope, the moon looks:
Why: A telescope collects more light and makes the moon look bigger and brighter.
3. What did Galileo see on the moon?
Why: Galileo saw the moon was rough, with bumps and hollows, not smooth.
Chapter review
Light and Seeing
0 / 6
1. What do your eyes need to see?
Why: Eyes only see when light reaches them. In a dark room you see nothing.
2. Which one is a light source?
Why: The sun makes its own light. The moon and a shoe only bounce light.
3. What makes a shadow?
Why: A shadow is the dark spot where light is blocked.
4. Which lets a little light through?
Why: Wax paper lets some light through as a glow. Wood and metal block it.
5. You tilt a mirror in the sun. The bright spot:
Why: Tilting the mirror changes where the light bounces. The spot moves.
6. Why does a telescope help you see the moon?
Why: A telescope gathers lots of light so faint, far things look bigger and brighter.
Send it to your teacher
★
Unit wrap-up
Light, Sound and Waves
Twelve words, twelve meanings
0 / 8
Tap a word, then tap its meaning. A right pair locks in green.
Words
Meanings
Unit test
Fifteen questions across the unit
0 / 10
1. Where does a sound come from?
Why: Every sound starts with a vibration, a fast shake. The shake spreads to your ear.
2. You press your hand on a ringing drum. The sound:
Why: Your hand stops the skin from shaking. No shaking means no sound.
3. Which sound is low?
Why: A big drum shakes slowly. Slow shaking makes a low sound.
4. Rice on a drum hops when you clap. What moved the rice?
Why: The clap sound spread through the air and shook the drum. The rice hopped.
5. Sound can travel through:
Why: Sound travels through air, through water and through solids like a table.
6. What do your eyes need to see?
Why: Eyes only work when light reaches them. In a dark room you see nothing.
7. Which one makes its own light?
Why: A flashlight is a light source. Rocks and books only bounce light.
8. A shadow is:
Why: When something blocks light, the place behind it stays dark. That is the shadow.
9. What does a mirror do to light?
Why: A mirror is smooth and shiny. Light bounces off it, so you see your face.
10. Which is a message sent with light?
Why: A lighthouse sends its message with light. Bells and whistles use sound.
Send it to your teacher
Spiral review
Five questions from earlier units
0 / 5
1. (Unit 1) Which is a property of a rock?
Why: A rock is hard. It does not pour or soak up water.
2. (Unit 1) A rolling ball bumps a still ball. What happens?
Why: Things that touch can push each other. The rolling ball pushes the still one.
3. (Unit 1) Why is paper a bad raincoat?
Why: Paper absorbs water. It gets soggy in the rain.
4. (Unit 1) You want a toy car to go far. What do you do?
Why: A big push makes a big change. The car goes far.
5. (Unit 1) A ball hits a wall and comes back. What did the wall do?
Why: The wall pushed back on the ball. That push changed its direction.
Send it to your teacher
Write it
Pick one: sound or light. Make a claim: how does it get from where it starts to you? Use two things you saw in this unit as evidence. Then tell why your evidence proves your claim.
Claim: say your idea in one short sentence.
Evidence: use the drum and the rice, or the lamp and the shadow.
Reasoning: tell why your evidence shows your claim is true.
Other side: what might a friend say? Why are they wrong?
0 wordsSaved on this device as you type.
Practice rooms
Rooms already on the site that belong to this unit — cards, quizzes, a lab.
Every lesson keeps its own three checks; a lesson is ticked when all three are right. Chapter reviews, the unit test and its spiral review (five questions from earlier units in this band) score on the page. When the site is connected to your sheet, or the link carries ?dest=, each one also has a Send box: the first-try score, the standards, the supports used, the attempt number and the minutes go to your sheet as an IEP data point.
Print this page for a paper copy of the readings, the sources, the words and the questions; the answers print as dashed boxes under each question.
Fact-check notes for this course live in the handoff: quotes marked (paraphrased) were set that way on purpose.