Elementary Science

The big picture

Today we will learn how to think like a scientist. A scientist asks questions and looks closely to find answers. The best part is that you can do this too, starting right now.

What is a scientist?

A scientist is a person who asks questions about the world and looks carefully to find the answers. A scientist is not just a grown-up in a white coat.

A scientist can be a kid watching ants on the sidewalk. A scientist can be you, wondering why the sky is blue.

Science is not just a big pile of facts. Science is a way of finding things out. Anyone who is curious can do it.

Key idea: A scientist is a curious person who asks questions and looks closely.

Start with a question

Science almost always starts with a question. A question is something you wonder about.

Good questions often start with these words:

• Why does the sky turn dark at night?
• How does a caterpillar turn into a butterfly?
• What happens if I put a plant in a dark closet?

There are no silly questions in science. Every big discovery started with someone being curious.

Key idea: Science begins when you wonder and ask a question.

Look closely: observing

Next, a scientist observes. To observe means to look, listen, smell, touch, or taste very carefully to learn about something.

You have five amazing tools for this. They are your five senses: sight, hearing, smell, touch, and taste.

Say you hold a lemon. It is yellow. It is bumpy. It smells fresh. It tastes sour. You just used four senses at once.

Good observing is slow. If I hand you a leaf, do not just say it is green. Keep looking. Is it dark green or light green? Are there tiny lines in it? Is one side shiny? A careful observer can find many things about one small leaf.

Key idea: To observe is to use your senses to notice things carefully.

An observation is not a guess

Here is a big idea. An observation is something you really sense. Wet grass is an observation. You can see it and feel it.

A guess is something you think might be true because of what you saw. You might think it rained last night. That is a guess.

Maybe you are right. Or maybe a sprinkler made the grass wet, not rain. A guess can be wrong even when the observation is right.

Good scientists keep observations and guesses in two separate baskets in their minds.

Key idea: What you saw is an observation. What you think it means is a guess.

The scientific method

Scientists follow a set of steps called the scientific method. It sounds fancy, but it is just a smart way to answer a question. Here are the steps in easy words:

1. Ask a question about something you notice.
2. Guess what you think the answer will be. This guess is called a hypothesis.
3. Test your guess by trying something or watching closely.
4. Observe and write down or draw what really happens.
5. Share what you learned with others.

Key idea: The scientific method is a step-by-step way to answer a question.

Let us try it: the sunny window

Let us walk through the steps, one at a time.

• Ask: Do plants grow taller near a window?
• Guess: Yes, because plants like light.
• Test: Put one bean plant on a sunny windowsill. Put another in a dark corner. Give both the same pot, the same soil, and the same water. Only the light is different.
• Observe: Each day, measure both plants with a ruler and write it down.
• Share: Tell your family what you found. Show them your chart.

Whatever happens, you learned something real. In science, there is no such thing as a failed experiment.

Key idea: You can test a real question by trying it and watching what happens.

A safe home experiment

Try this. Get one small object from your kitchen, like an apple or a cracker.

1. Look at it. Write down two things you see.
2. Smell it. Write down what it smells like.
3. Touch it. Is it smooth or bumpy?

You will be surprised how much you can notice about one small thing. That is what scientists do all day.

Key idea: Slow, careful looking helps you learn a lot.

Watch out for

• Thinking only grown-ups in white coats are scientists. A curious kid is a scientist too.
• Thinking a wrong guess means you did something wrong. A wrong guess is a real discovery.
• Thinking observing means only looking with your eyes. You can also listen, smell, and touch.
• Mixing up what you saw with what you think it means.

Recap

• A scientist asks questions and observes to learn about the world.
• Science starts with a question that you can test.
• To observe is to use your five senses carefully.
• An observation is what you sense. A guess is what you think it means.
• The scientific method is: ask, guess, test, observe, share.

Sources

1. National Geographic Kids, Science section, kids.nationalgeographic.com
2. Mystery Science, Getting Started With Science lessons, mysteryscience.com
3. PBS LearningMedia, Scientific Method resources, pbslearningmedia.org

The big picture

Today we will learn how to do a fair experiment. An experiment is a test you set up to answer a question. You can do many fun ones right at home.

What is an experiment?

An experiment is a test you plan to find an answer. You change one thing on purpose and watch what happens.

Scientists do experiments to check their guesses. You can do them with things around your house.

Key idea: An experiment is a planned test to answer a question.

What makes a test fair?

A good experiment is a fair test. In a fair test, you change only one thing. You keep everything else the same.

Say you want to know if plants grow better with water or with soda. You give one plant water and one plant soda.

To be fair, both plants need the same pot, the same soil, the same light, and the same sunny spot. Only the drink is different.

If you changed two things at once, you would not know which one caused the change. That is why we change just one.

Key idea: In a fair test, you change only one thing and keep the rest the same.

The one thing you change

The one thing you change is called the variable. A variable is the part of an experiment that you change on purpose.

In the plant test, the drink is the variable. Water or soda, that is the thing you are testing.

Key idea: The variable is the one thing you change on purpose.

Measure and write it down

Scientists do not just look once. They measure, which means to find out how much or how big using a tool.

You can measure with a ruler, a cup, a clock, or a scale. Measuring turns a guess like taller into a number like 12 centimeters.

Then write it down in a chart or a notebook. Writing helps you remember and compare.

• Day 1: 5 centimeters
• Day 3: 7 centimeters
• Day 5: 9 centimeters

Key idea: Measuring and writing it down helps you see what really happened.

Do it more than once

One try can happen by luck. If you flip a coin once and get heads, that does not prove coins always land on heads.

So scientists repeat their tests. To repeat means to do it again to check. If you get the same answer many times, you can trust it more.

Key idea: Doing a test more than once helps you trust the answer.

A safe home experiment: sink or float

Here is a fun one you can do with a bowl of water. Ask a grown-up if you can use the sink.

1. Fill a bowl with water.
2. Gather small safe things: a coin, a cork, a plastic spoon, a grape, a paperclip.
3. Before you drop each one, guess: will it sink or float?
4. Drop it in and watch. Write down what really happened.

You will find that some heavy-feeling things float and some light things sink. That is a great new question to explore.

Key idea: Guessing first, then testing, is exactly how scientists work.

Stay safe

Real scientists stay safe. So do you.

• Ask a grown-up before you start.
• Never taste things unless a grown-up says it is safe food.
• Clean up spills so no one slips.
• Wash your hands when you finish.

Key idea: Being safe is part of being a good scientist.

Watch out for

• Changing two things at once. Then you cannot tell what caused the result.
• Only looking once. Do it again to be sure.
• Forgetting to write things down. Your memory can trick you.
• Thinking a surprising result is a mistake. A surprise is a new discovery.

Recap

• An experiment is a planned test to answer a question.
• A fair test changes only one thing and keeps the rest the same.
• The one thing you change is the variable.
• Measure with tools and write it down.
• Repeat your test so you can trust the answer.

Sources

1. Mystery Science, Doing Experiments lessons, mysteryscience.com
2. National Geographic Kids, Science section, kids.nationalgeographic.com
3. PBS LearningMedia, Fair Tests and Variables, pbslearningmedia.org

The big picture

Today we will learn the difference between living things and nonliving things. A dog is living. A rock is nonliving. Learning to tell them apart is one of the first big jobs in science.

What is a living thing?

A living thing is something that is alive. It grows, needs food and water, and can make more of its own kind.

Dogs, cats, trees, flowers, fish, birds, and people are all living things. You are a living thing.

Even tiny things too small to see, like the germs on your hands, are living.

Key idea: A living thing is alive. It grows, eats, and can make more of its kind.

What is a nonliving thing?

A nonliving thing is something that is not alive. It does not grow on its own, and it does not need food or water.

Rocks, water, toys, chairs, spoons, and clouds are nonliving. A teddy bear is nonliving, even though it looks like an animal.

Key idea: A nonliving thing is not alive and does not need food or water.

What do living things do?

Living things all share some special jobs. Here are the big ones:

• Grow: A puppy grows into a big dog. A seed grows into a plant.
• Need food and water: Living things must eat and drink to stay alive.
• Breathe: Most living things need air.
• Move: Animals walk or swim. Even plants slowly turn toward the light.
• Sense things: Living things can feel or notice the world around them.
• Make more of their kind: Cats have kittens. Trees make seeds.

Key idea: Living things grow, eat, breathe, move, sense, and make more of their kind.

What do living things need?

Every living thing needs a few things to stay alive:

• Food, to give them energy.
• Water, to drink.
• Air, to breathe.
• A safe place to live.

Plants make their own food from sunlight, but they still need water, air, and light. We will learn how in the next lesson.

Key idea: Living things need food, water, air, and a safe place.

Tricky ones

Some things can trick you. A car moves and needs gas, but it is nonliving. It cannot grow or have baby cars.

A river moves too, but it is nonliving. Moving alone does not mean something is alive.

A seed looks still, like a tiny stone. But a seed is alive. If you give it soil and water, it grows.

A fallen leaf was once part of a living tree. Now it is dead, so it is no longer living.

Key idea: Moving alone does not make something alive. Look for growing, eating, and making more.

A safe home experiment: sort your room

Try this at home. It is easy and fun.

1. Walk around one room with a grown-up.
2. Point to five things. For each one, say living or nonliving.
3. For living things, name one thing it needs, like food or water.
4. A pet and a houseplant are living. A lamp and a pillow are nonliving.

Key idea: You can sort the whole world into living and nonliving things.

Watch out for

• Thinking that anything that moves is alive. Cars and rivers move but are not alive.
• Thinking a seed is nonliving because it sits still. A seed is alive.
• Thinking a teddy bear is alive because it looks like an animal.
• Forgetting that plants are living things too.

Recap

• A living thing is alive. It grows, eats, breathes, and can make more of its kind.
• A nonliving thing is not alive and does not need food or water.
• Living things need food, water, air, and a safe place.
• Moving alone does not make something alive.

Sources

1. National Geographic Kids, Animals and Nature, kids.nationalgeographic.com
2. Mystery Science, Living Things lessons, mysteryscience.com
3. PBS LearningMedia, Living and Nonliving resources, pbslearningmedia.org

The big picture

Today we will learn how plants grow. Plants start as tiny seeds and turn into big green living things. They even make their own food from sunlight, which is one of the coolest tricks in nature.

The parts of a plant

Most plants have the same main parts. Each part has a special job.

• Roots: The roots grow down into the soil. They drink up water and hold the plant in place.
• Stem: The stem holds the plant up. It carries water from the roots to the leaves.
• Leaves: The leaves catch sunlight and make food for the plant.
• Flowers: Many plants grow flowers that make seeds for new plants.

Key idea: Roots drink water, the stem holds the plant up, and leaves catch sunlight.

How plants make food

Here is something amazing. Plants make their own food. They do it in a process called photosynthesis.

Photosynthesis is when a plant uses sunlight, water, and air to make its own food. The green leaves do most of the work.

Think of a leaf like a tiny kitchen. It takes in sunlight from above, water from the roots, and air from around it. Then it makes sugar, which is the plant food.

Plants even give off fresh air for us to breathe while they do this. That is why plants and trees are so important.

Key idea: Photosynthesis is how plants use sunlight, water, and air to make their own food.

What plants need to grow

To grow big and healthy, a plant needs four things:

1. Sunlight, to make food.
2. Water, which the roots drink up.
3. Air, which the leaves use.
4. Soil, which holds the roots and gives the plant helpful bits called nutrients.

If a plant is missing one of these, it may grow weak or turn yellow. Try to give plants all four.

Key idea: Plants need sunlight, water, air, and soil to grow.

From seed to plant: the life cycle

A plant grows in steps. These steps are called a life cycle. A life cycle is the path a living thing takes from its start to when it makes new life.

1. A seed rests in the soil. A seed is a tiny package that holds a baby plant.
2. With water and warmth, the seed sprouts. A little root goes down and a green shoot goes up.
3. The young plant grows a stem and leaves.
4. The grown plant makes flowers.
5. The flowers make new seeds, and the cycle starts again.

Key idea: A plant grows from a seed, into a plant, into flowers, and then makes new seeds.

How seeds travel

Seeds need to move away from the parent plant to find their own space, sun, and soil. Nature helps them travel.

• Wind blows light seeds, like a dandelion puff, through the air.
• Animals eat fruit and drop the seeds far away.
• Some seeds have little hooks that stick to fur or socks.
• Water carries some seeds down a stream.

Key idea: Wind, animals, and water help seeds travel to new places.

A safe home experiment: grow a bean

You can watch a seed grow. Ask a grown-up for a dried bean and a clear cup.

1. Fold a wet paper towel and put it inside the clear cup.
2. Tuck a bean between the towel and the side of the cup, so you can see it.
3. Keep the towel damp and put the cup in a warm, bright spot.
4. Watch each day. In about a week, you will see a root and a green shoot.

Key idea: With water and warmth, a seed will sprout right before your eyes.

Watch out for

• Thinking plants eat food from the soil like we eat dinner. Plants make their own food from sunlight.
• Thinking roots are not important because you cannot see them. Roots drink the water.
• Thinking a plant can live in a dark closet. Plants need light to make food.
• Thinking seeds are not alive. A seed holds a baby plant and is living.

Recap

• Plants have roots, a stem, leaves, and often flowers.
• Photosynthesis is how plants make food from sunlight, water, and air.
• Plants need sunlight, water, air, and soil.
• A plant grows from a seed and later makes new seeds.
• Wind, animals, and water help seeds travel.

Sources

1. National Geographic Kids, Plants section, kids.nationalgeographic.com
2. Mystery Science, Plant Growth lessons, mysteryscience.com
3. PBS LearningMedia, Plant Life Cycle resources, pbslearningmedia.org

The big picture

Today we will explore where animals live and how their bodies fit their homes. A polar bear could not live in a hot desert, and a camel could not live on the ice. Every animal has a home that is just right for it.

What is a habitat?

A habitat is the place where an animal lives. It is the animal's home in nature.

A habitat gives an animal what it needs: food, water, air, and a safe place to rest and raise babies.

There are many kinds of habitats: forests, deserts, oceans, ponds, grasslands, and icy poles.

Key idea: A habitat is the place where an animal finds food, water, and shelter.

Different homes for different animals

Each habitat is home to animals that fit it well.

• Ocean: Fish, whales, and crabs live in the salty water.
• Desert: Camels, lizards, and snakes live where it is hot and dry.
• Forest: Deer, owls, and bears live among the trees.
• Cold poles: Polar bears and penguins live on the ice.
• Pond: Frogs, ducks, and turtles live in and near the water.

Key idea: Different habitats are home to different animals.

How animals fit their homes

Animals have special body parts that help them live in their habitat. These helpful features are called adaptations. An adaptation is a body part or a habit that helps an animal live where it does.

• A polar bear has thick fur and fat to stay warm on the ice.
• A camel can go a long time without water in the hot desert.
• A duck has webbed feet that work like paddles for swimming.
• A fish has gills to breathe under water.
• A giraffe has a long neck to reach leaves high in the trees.

Key idea: An adaptation is a body part or habit that helps an animal live in its home.

What do animals eat?

Animals eat different foods. We can sort them into three groups.

• Herbivores eat plants. A herbivore is a plant eater, like a rabbit or a cow.
• Carnivores eat other animals. A carnivore is a meat eater, like a lion or a shark.
• Omnivores eat both plants and animals. An omnivore eats both, like a bear or a person.

Key idea: Animals can be plant eaters, meat eaters, or both.

How animals stay safe

Animals have clever ways to stay safe from other animals that want to eat them.

• Camouflage is a color or pattern that helps an animal hide. A green frog blends into green leaves.
• A turtle hides inside its hard shell.
• A skunk makes a bad smell to scare others away.
• A rabbit runs fast and zigzags.

Key idea: Animals hide, run, or protect themselves to stay safe.

When homes change

Animals depend on their habitat. If the habitat changes too much, animals can lose their home.

When people cut down a forest or pollute a river, the animals there may have nowhere to live.

This is why keeping habitats clean and safe helps animals. We will learn more about caring for the Earth later.

Key idea: Animals need their habitats, so keeping habitats safe helps animals.

A safe home activity: watch a habitat

You do not need to travel far to study a habitat. Try this.

1. Sit quietly in a yard, a park, or by a window for five minutes.
2. Watch for animals: birds, bugs, squirrels, or worms.
3. Write down what each one does. Where does it hide? What does it eat?
4. Think about how its body helps it live there.

Key idea: Even a backyard is a habitat full of animals to observe.

Watch out for

• Thinking any animal can live anywhere. A polar bear cannot live in a desert.
• Thinking adaptations happen on purpose in one day. They build up slowly over many, many animal lifetimes.
• Thinking camouflage means an animal is invisible. It just helps it blend in and hide.
• Forgetting that people can change habitats too.

Recap

• A habitat is the place where an animal lives and finds what it needs.
• Different animals live in different habitats.
• Adaptations are body parts or habits that help an animal fit its home.
• Animals can be herbivores, carnivores, or omnivores.
• Animals hide, run, or protect themselves to stay safe.

Sources

1. National Geographic Kids, Animals section, kids.nationalgeographic.com
2. Smithsonian's National Zoo and Conservation Biology Institute, nationalzoo.si.edu
3. PBS LearningMedia, Animal Habitats resources, pbslearningmedia.org

The big picture

Today we will explore your amazing body. Your body has many parts that work together like a team. Even while you sleep, your heart beats and your lungs breathe, all by themselves.

Your body is a team

Your body is made of many parts. Some you can see, like your arms and legs. Some are inside, like your heart and stomach.

Groups of parts that work together to do a job are called systems. A system is a team of body parts with one big job.

Key idea: Your body is a team of parts that work together in systems.

Your bones and muscles

Inside you is a frame of hard parts called bones. Bones are the hard parts that hold up your body and keep its shape. All your bones together make your skeleton.

Bones also keep soft parts safe. Your skull is a bony helmet for your brain. Your ribs make a cage that protects your heart and lungs.

Your muscles are the soft parts that pull on your bones to make you move. Muscles work when you run, smile, or wave.

Key idea: Bones hold you up and keep you safe. Muscles pull on bones to make you move.

Your heart and blood

Your heart is a strong muscle in your chest. Its job is to pump blood all around your body.

Blood carries food and air to every part of you. Your heart beats all day and all night, without you telling it to.

Put your hand on your chest and you may feel it. Run around, and your heart beats faster to give your body more.

Key idea: Your heart pumps blood, which carries food and air all through your body.

Your lungs and breathing

Your lungs are two soft parts in your chest that fill with air when you breathe. You have two of them.

When you breathe in, your lungs take in fresh air. Your body uses a part of that air, called oxygen, to stay alive.

When you breathe out, your lungs push out air your body does not need. You breathe about 20,000 times a day.

Key idea: Your lungs bring in fresh air so your body can use it.

Your brain

Your brain is the control center of your body. It sits inside your head, kept safe by your skull.

Your brain lets you think, learn, remember, and feel. It also tells your muscles to move and keeps your heart and lungs going.

Your brain talks to the rest of your body through tiny message lines called nerves. The messages zoom faster than you can blink.

Key idea: Your brain is the control center that helps you think and move.

Your stomach and food

When you eat, your food goes down to your stomach. The stomach is the part that breaks down food after you swallow.

Your body takes the good parts of the food to give you energy to run and grow. This whole trip is called digestion.

Key idea: Your stomach breaks down food so your body can use it for energy.

Taking care of your body

Your body works hard for you. Here is how to help it stay healthy:

• Eat healthy foods like fruits and vegetables.
• Drink water.
• Run and play to keep your heart and muscles strong.
• Sleep well so your body can rest and grow.
• Wash your hands to keep germs away.

Key idea: Healthy food, water, play, sleep, and clean hands keep your body strong.

A safe home activity: feel your heartbeat

Try this to feel your body at work.

1. Sit still and put your hand on your chest. Feel your heartbeat.
2. Now jump up and down 20 times.
3. Put your hand back on your chest. Is your heart beating faster?
4. It beats faster to give your busy muscles more blood.

Key idea: Your heart speeds up when you move, to help your body.

Watch out for

• Thinking your heart looks like a red paper heart. A real heart is a strong muscle the size of your fist.
• Thinking you breathe only through your mouth. You breathe through your nose too.
• Thinking bones are dry sticks. Living bones are strong and even a little bendy.
• Thinking your brain rests when you sleep. It keeps your heart and lungs going all night.

Recap

• Your body is a team of parts that work in systems.
• Bones hold you up and protect you. Muscles make you move.
• Your heart pumps blood. Your lungs bring in air.
• Your brain is the control center.
• Your stomach breaks down food for energy.

Sources

1. National Geographic Kids, Human Body section, kids.nationalgeographic.com
2. PBS LearningMedia, Human Body resources, pbslearningmedia.org
3. Smithsonian Science Education Center, ssec.si.edu

The big picture

Today we will learn what everything is made of. A rock, a glass of milk, and the air you breathe are all made of matter. Matter comes in three main forms, and water can be all three.

What is matter?

Matter is anything that takes up space and has weight. Your chair is matter. Water is matter. Even the air around you is matter.

Almost everything you can think of is made of matter. Matter comes in three main forms called states: solid, liquid, and gas.

Key idea: Matter is anything that takes up space and has weight.

Solids

A solid is matter that keeps its own shape. A block, a spoon, and a rock are solids.

If you put a solid in a box, it keeps its shape. A toy car is a car in your hand or in a bowl. It does not spread out.

Solids can be hard like a rock or soft like a pillow, but they all hold their shape.

Key idea: A solid keeps its own shape.

Liquids

A liquid is matter that flows and takes the shape of its container. Water, milk, and juice are liquids.

Pour a liquid into a round cup, and it becomes round. Pour it into a tall glass, and it becomes tall. A liquid changes shape but keeps the same amount.

Liquids can be poured and spilled. That is why we keep them in cups and bottles.

Key idea: A liquid flows and takes the shape of its container.

Gases

A gas is matter that spreads out to fill all the space it can. Air is a gas. The bubbles in soda are gas.

You often cannot see a gas, but it is there. When you blow up a balloon, gas fills it and makes it puff out.

Gas does not keep a shape and does not stay in one spot. It floats and spreads everywhere.

Key idea: A gas spreads out to fill all the space it can.

Water can be all three

Here is something cool. Water can be a solid, a liquid, or a gas.

• Solid: When water gets very cold, it freezes into ice.
• Liquid: When ice warms up, it melts into water you can pour.
• Gas: When water gets very hot, it boils into steam, called water vapor.

It is still water the whole time. Only its form changes.

Key idea: Water can be ice, liquid water, or steam, depending on how hot or cold it is.

How matter changes form

What makes matter change form? Heat.

• Adding heat can melt a solid into a liquid, like ice into water.
• More heat can boil a liquid into a gas, like water into steam.
• Taking heat away can freeze a liquid into a solid, like water into ice.

Key idea: Adding or taking away heat can change matter from one form to another.

A safe home experiment: melt an ice cube

You can watch matter change form. Ask a grown-up for an ice cube.

1. Put an ice cube (a solid) on a plate.
2. Leave it on the counter and watch.
3. Soon it melts into a puddle of water (a liquid).
4. If you leave the puddle for many hours, some of it dries up into the air as gas.

Key idea: One ice cube can show you a solid, a liquid, and even a gas.

Watch out for

• Thinking gas is not real because you cannot see it. Air is a gas and it is all around you.
• Thinking a liquid changes its amount when it changes shape. It only changes shape.
• Thinking melted ice is a new thing. It is still water, just in liquid form.
• Thinking only hard things are solids. A soft pillow is a solid too.

Recap

• Matter is anything that takes up space and has weight.
• A solid keeps its own shape.
• A liquid flows and takes the shape of its container.
• A gas spreads out to fill its space.
• Heat can change matter from one form to another.

Sources

1. National Geographic Kids, Science section, kids.nationalgeographic.com
2. Mystery Science, States of Matter lessons, mysteryscience.com
3. PBS LearningMedia, Solids Liquids and Gases resources, pbslearningmedia.org

The big picture

Today we will learn what makes things move and stop. Every time you kick a ball or open a door, you are using a force. Forces are pushes and pulls, and they are all around us.

What is a force?

A force is a push or a pull. A force can make something start to move, stop, speed up, slow down, or change direction.

When you push a swing, that is a force. When you pull a wagon, that is a force too.

Key idea: A force is a push or a pull that can make things move or stop.

Pushes and pulls

There are two main kinds of force.

• A push moves something away from you. You push a shopping cart or push a door shut.
• A pull moves something toward you. You pull a drawer open or pull a rope in tug of war.

Look around and you will see pushes and pulls everywhere.

Key idea: A push moves things away and a pull moves things toward you.

Big force and small force

Forces can be big or small. A big force moves things more. A small force moves things less.

A gentle tap sends a ball a short way. A hard kick sends it far. The bigger the push, the more the ball moves.

Key idea: A bigger force makes a bigger change in how something moves.

Gravity: the pull of the Earth

Here is a force you feel all the time. Gravity is the pull that brings things down toward the Earth.

When you drop a ball, gravity pulls it to the floor. When you jump, gravity brings you back down.

Gravity is why things fall. It keeps you on the ground instead of floating away. It even holds the Moon near the Earth.

Key idea: Gravity is the pull that brings things down toward the Earth.

Friction: the force that slows things down

Friction is a force that slows things down when they rub together. It happens when two things touch and move against each other.

Roll a ball on grass and it stops quickly, because grass has a lot of friction. Roll it on smooth ice and it slides far, because ice has little friction.

Friction is helpful. It lets your shoes grip the floor so you do not slip. It helps a bike stop when you use the brakes.

Key idea: Friction is a force that slows things down when they rub together.

Magnets: a special pull

A magnet is an object that can pull certain metals toward it without even touching them. Magnets pull on things made of iron and steel.

A magnet can hold a paper on the fridge. Magnets have two ends, called poles. Two magnets can pull together or push apart.

Key idea: A magnet can pull certain metals toward it.

A safe home experiment: ramp race

You can see forces at work with a ramp. Ask a grown-up if you can use a book and a toy car.

1. Lean a book on a pillow to make a small ramp.
2. Let a toy car roll down. Gravity pulls it down the ramp.
3. Now make the ramp steeper. Does the car go faster?
4. Try rolling it onto a rug and onto a smooth floor. Friction stops it faster on the rug.

Key idea: Gravity pulls the car down, and friction slows it to a stop.

Watch out for

• Thinking things move on their own. Something always pushes or pulls them.
• Thinking heavy things fall faster than light things. Gravity pulls on all of them.
• Thinking friction is bad. Friction helps you walk and stop.
• Thinking magnets pull everything. They only pull certain metals like iron and steel.

Recap

• A force is a push or a pull.
• A push moves things away. A pull moves things toward you.
• A bigger force makes a bigger change in motion.
• Gravity pulls things down toward the Earth.
• Friction slows things down when they rub together.

Sources

1. National Geographic Kids, Science section, kids.nationalgeographic.com
2. Mystery Science, Forces and Motion lessons, mysteryscience.com
3. PBS LearningMedia, Forces and Motion resources, pbslearningmedia.org

The big picture

Today we will learn about energy. Energy is what makes things happen. It lights our rooms, warms our food, and lets us hear music. You use energy every second of the day.

What is energy?

Energy is the power to make things happen or to do work. Energy can make things move, glow, get warm, or make sound.

You have energy from the food you eat. A car gets energy from fuel. A lamp gets energy from electricity.

Most of the energy on Earth comes from one big source: the Sun.

Key idea: Energy is the power to make things happen.

Light energy

Light is a kind of energy that lets us see. Without light, everything would be dark.

The Sun is our biggest source of light. We also get light from lamps, flashlights, and fire.

Light travels in straight lines. When light hits something it cannot pass through, it makes a dark spot behind it called a shadow. A shadow is the dark shape made when something blocks light.

Key idea: Light is energy that lets us see, and it makes shadows when it is blocked.

Heat energy

Heat is a kind of energy that makes things warm. The Sun gives us heat. So does a stove, a fire, and even your own body.

Heat moves from warm things to cold things. That is why a warm cup of cocoa slowly cools down, and why an ice cube in your hand melts.

Heat can also change matter, like melting ice into water or cooking an egg.

Key idea: Heat is energy that makes things warm and moves from warm to cold.

Sound energy

Sound is a kind of energy that we hear with our ears. Every sound is made by something moving back and forth very fast. That fast back-and-forth movement is called a vibration.

When you pluck a guitar string, it vibrates and makes a sound. When you talk, parts inside your throat vibrate.

Sound travels through the air to reach your ears. Big vibrations make loud sounds. Small vibrations make soft sounds.

Key idea: Sound is energy made by vibrations, and we hear it with our ears.

Energy can change form

Energy can change from one kind to another. This is a big idea in science.

• A lamp changes electricity into light and a little heat.
• A fire changes wood into light and heat.
• A radio changes electricity into sound.
• Your body changes food into the energy to run and play.

Key idea: Energy can change from one form into another.

Where energy comes from

We use energy every day. It comes from many places.

• The Sun gives light and heat.
• Food gives energy to living things.
• Electricity powers lights and machines in our homes.
• Wind and moving water can make electricity too.

Key idea: Energy comes from the Sun, food, electricity, wind, and water.

A safe home experiment: feel the vibration

You can feel sound energy. Try this.

1. Gently rest your fingers on the front of your throat.
2. Hum a long note. Can you feel the buzzing?
3. That buzzing is a vibration making sound.
4. Now stretch a rubber band and pluck it. Watch it wiggle and listen to the sound.

Key idea: Sound comes from vibrations you can sometimes feel and see.

Watch out for

• Thinking you can see in the dark. Your eyes need light to see.
• Thinking cold moves into warm things. Really, heat moves out of warm things.
• Thinking sound can happen without movement. Every sound comes from a vibration.
• Thinking energy disappears. It usually just changes into another form.

Recap

• Energy is the power to make things happen.
• Light is energy that lets us see and makes shadows.
• Heat is energy that makes things warm.
• Sound is energy made by vibrations.
• Energy can change from one form to another.

Sources

1. National Geographic Kids, Science section, kids.nationalgeographic.com
2. Mystery Science, Energy and Sound lessons, mysteryscience.com
3. PBS LearningMedia, Light Heat and Sound resources, pbslearningmedia.org

The big picture

Today we will learn about our Earth and its weather. Is it sunny, rainy, windy, or snowy today? Weather changes all the time, and learning to read the sky is a real science skill.

What is weather?

Weather is what the sky and air are like at one place and time. Weather can be sunny, cloudy, rainy, windy, snowy, or foggy.

Weather can change from morning to afternoon. It can be different in two towns on the same day.

Key idea: Weather is what the sky and air are like right now.

Weather and temperature

One big part of weather is how warm or cold it is. We call this the temperature. Temperature is a measure of how hot or cold something is.

We use a tool called a thermometer to measure temperature. On a hot day, the temperature is high. On a cold day, it is low.

Key idea: Temperature tells us how hot or cold the air is.

Clouds and rain

Clouds are made of tiny drops of water floating in the sky. When the drops join and grow big and heavy, they fall as rain.

When it is very cold, the water freezes and falls as snow. Sometimes it falls as tiny ice balls called hail.

Rain, snow, and hail are all called precipitation. Precipitation is water that falls from the sky.

Key idea: Rain, snow, and hail are precipitation, which is water falling from the sky.

Wind

Wind is moving air. You cannot see wind, but you can feel it and see what it does.

Wind can be a gentle breeze that cools your face. It can also be a strong gust that bends the trees.

Wind pushes clouds across the sky, flies kites, and turns pinwheels.

Key idea: Wind is moving air that we can feel but not see.

The four seasons

Weather also changes with the seasons. A season is a time of year with its own kind of weather. There are four seasons.

• Spring: It gets warmer, rain falls, and plants start to grow.
• Summer: It is hot and often sunny.
• Fall: It gets cooler and many leaves change color and drop.
• Winter: It is cold, and in some places it snows.

The seasons happen because the Earth is tilted as it travels around the Sun.

Key idea: The four seasons are spring, summer, fall, and winter, each with its own weather.

Weather and climate are different

Weather is what happens today. Climate is the usual weather of a place over many years.

A rainy Tuesday is weather. The fact that a desert is usually dry all year is its climate.

Key idea: Weather is today. Climate is the usual weather over many years.

Why weather matters

Weather helps us decide what to do. We check it to know what to wear and whether to bring an umbrella.

Farmers watch weather to know when to plant. Pilots check it to fly safely. Weather forecasters use tools to guess tomorrow's weather.

Key idea: People watch weather to stay safe and plan their day.

A safe home activity: be a weather watcher

You can track weather like a scientist. Try this for a week.

1. Each morning, look out the window.
2. Draw a picture of the sky: sun, clouds, or rain.
3. Is it warm or cold? Windy or still?
4. After a week, look back. What days were alike? What changed?

Key idea: Watching the sky each day helps you learn how weather changes.

Watch out for

• Mixing up weather and climate. Weather is today. Climate is over many years.
• Thinking clouds are made of cotton or smoke. They are made of tiny water drops.
• Thinking wind is not real because you cannot see it. Wind is moving air you can feel.
• Thinking it is the same weather everywhere. It can differ from town to town.

Recap

• Weather is what the sky and air are like right now.
• Temperature tells us how hot or cold it is.
• Rain, snow, and hail are precipitation.
• Wind is moving air.
• The four seasons are spring, summer, fall, and winter.

Sources

1. National Geographic Kids, Weather section, kids.nationalgeographic.com
2. Mystery Science, Weather lessons, mysteryscience.com
3. PBS LearningMedia, Weather and Seasons resources, pbslearningmedia.org

The big picture

Today we will follow a drop of water on an amazing journey. The same water goes up to the sky, forms clouds, and falls back down as rain, over and over. This never-ending trip is called the water cycle.

Water is always moving

The water on Earth is always on the move. It goes from the oceans and lakes, up into the sky, and back down again.

This journey happens again and again, so we call it the water cycle. A cycle is something that repeats over and over.

The amazing part is that the Earth reuses the same water. The rain today may have been in an ocean last week.

Key idea: The water cycle is the never-ending journey water takes from the ground to the sky and back.

Step 1: Evaporation

The Sun warms the water in oceans, lakes, and puddles. When water gets warm, it turns into a gas called water vapor and floats up into the air. This is called evaporation.

Evaporation is when water changes from a liquid into a gas and rises into the sky. You cannot see water vapor, but it is there.

This is why a wet sidewalk dries up on a sunny day. The water did not vanish. It evaporated into the air.

Key idea: Evaporation is when the Sun warms water and it rises into the air as a gas.

Step 2: Condensation

High up in the sky, the air is cold. The cold air makes the water vapor turn back into tiny water drops. This is called condensation.

Condensation is when water vapor cools and turns back into little drops. Those tiny drops gather together to make clouds.

You can see condensation at home. When you take a cold drink out on a warm day, drops form on the outside of the glass.

Key idea: Condensation is when water vapor cools and turns back into drops, making clouds.

Step 3: Precipitation

The tiny drops in a cloud bump into each other and grow bigger. When they get too big and heavy to float, they fall down. This is called precipitation.

Precipitation is water that falls from the sky. It can be rain, or if it is cold, snow, sleet, or hail.

Key idea: Precipitation is when the drops grow heavy and fall from the sky as rain or snow.

Step 4: Collection

When the water falls, it lands on the ground. It flows into rivers, lakes, and oceans, or it soaks into the soil. This is called collection.

Then the Sun warms this water again, and the whole cycle starts over. Around and around it goes.

Key idea: Collection is when fallen water gathers in oceans, lakes, and rivers, ready to start again.

The cycle goes round and round

Let us put the four steps together:

1. Evaporation: The Sun warms water and it rises as gas.
2. Condensation: The gas cools and makes clouds.
3. Precipitation: Water falls as rain or snow.
4. Collection: Water gathers in oceans and lakes, and it starts again.

This cycle has been going for millions of years. It gives us the fresh water we drink.

Key idea: The four steps repeat forever: evaporate, condense, precipitate, collect.

A safe home experiment: make rain in a cup

You can watch the water cycle with a grown-up's help.

1. Ask a grown-up to pour warm water into a clear cup, about halfway.
2. Put a plate on top of the cup.
3. Place a few ice cubes on the plate.
4. Watch. The warm water evaporates, hits the cold plate, condenses into drops, and rains back down.

Key idea: Warm water plus a cold surface makes tiny rain, just like the sky.

Watch out for

• Thinking rain is brand new water. It is the same water, reused over and over.
• Thinking a puddle that dries up just vanished. It evaporated into the air.
• Mixing up the words. Evaporation goes up. Precipitation comes down.
• Thinking clouds are solid. They are made of tiny water drops.

Recap

• The water cycle is the never-ending journey of water.
• Evaporation: the Sun warms water and it rises as gas.
• Condensation: the gas cools and forms clouds.
• Precipitation: water falls as rain or snow.
• Collection: water gathers, and the cycle starts again.

Sources

1. USGS Water Science School, The Water Cycle, usgs.gov
2. NASA Space Place, Water and climate, spaceplace.nasa.gov
3. National Geographic Kids, Water section, kids.nationalgeographic.com

The big picture

Today we will blast off into space to explore our solar system. Our Earth is one of eight planets that travel around the Sun. Space is huge, and it is full of amazing things to discover.

What is the solar system?

The solar system is the Sun and everything that travels around it. That includes eight planets, their moons, and many smaller rocks.

The Sun sits in the middle. Everything else circles around it.

Key idea: The solar system is the Sun and everything that travels around it.

The Sun is a star

The Sun is a star. A star is a huge ball of hot, glowing gas. The Sun looks small because it is very far away, but it is really enormous.

The Sun gives us light and heat. Without it, Earth would be dark, frozen, and empty.

Never look straight at the Sun. Its light is so strong it can hurt your eyes.

Key idea: The Sun is a star that gives Earth light and heat.

What is a planet?

A planet is a large, round object that travels around the Sun. The path a planet takes around the Sun is called its orbit.

There are eight planets. In order from the Sun, they are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

Key idea: A planet is a large, round object that orbits, or travels around, the Sun.

Our home planet: Earth

Earth is the third planet from the Sun, and it is our home. As far as we know, it is the only planet with living things on it.

Earth is just the right distance from the Sun. It is not too hot and not too cold. It has air to breathe and water to drink.

Key idea: Earth is our home planet, with air, water, and life.

The Moon

The Moon is a big ball of rock that travels around the Earth. It is our closest neighbor in space.

The Moon does not make its own light. It shines because sunlight bounces off it.

The Moon seems to change shape through the month. These shapes are called phases. Really the Moon is round the whole time. We just see different amounts of its lit side.

Key idea: The Moon is a ball of rock that circles Earth and reflects the Sun's light.

Stars and space

At night, you can see tiny points of light in the sky. Most of those are stars, just like our Sun, but so far away they look tiny.

There are more stars than anyone can count. Our Sun is only one of them.

Big groups of stars make up a galaxy. Our galaxy is called the Milky Way.

Key idea: Stars are faraway suns, and huge groups of them form galaxies.

Day and night

Why do we have day and night? The Earth spins around like a top. This spinning is called rotation.

As the Earth spins, one side faces the Sun and has day. The other side faces away and has night. One full spin takes 24 hours, which is one day.

Key idea: Day and night happen because the Earth spins around.

A safe home activity: be the Earth

You can act out day and night. Ask a grown-up to help.

1. Put a lamp in the middle of a room. The lamp is the Sun.
2. You are the Earth. Stand facing the lamp. Your face is in daytime.
3. Slowly spin around in place.
4. When your face turns away from the lamp, that is nighttime.

Key idea: Spinning shows how one Earth can have day on one side and night on the other.

Watch out for

• Thinking the Sun moves around the Earth. Really, the Earth spins and orbits the Sun.
• Thinking the Moon makes its own light. It reflects sunlight.
• Thinking stars are small. They are huge suns that are very far away.
• Thinking the Moon changes its real shape. We just see different parts lit up.

Recap

• The solar system is the Sun and everything that orbits it.
• The Sun is a star that gives us light and heat.
• There are eight planets, and Earth is our home.
• The Moon circles Earth and reflects sunlight.
• Day and night happen because the Earth spins.

Sources

1. NASA Space Place, Solar System, spaceplace.nasa.gov
2. National Geographic Kids, Space section, kids.nationalgeographic.com
3. PBS LearningMedia, Solar System resources, pbslearningmedia.org

The big picture

Today we will learn how to take care of our planet. The Earth is the only home we have, and it gives us everything we need. There are simple things kids can do every day to keep it clean and healthy.

Why our planet needs our help

The Earth gives us air, water, food, and a home for all living things. We need to take good care of it.

Sometimes people make too much trash or make the air and water dirty. Dirty air and water are called pollution. Pollution is anything that makes the land, air, or water unclean.

Pollution can hurt plants, animals, and people. The good news is that we can all help stop it.

Key idea: The Earth is our only home, and we can help keep it clean.

The three Rs

There are three easy words that help us take care of the Earth. They all start with the letter R: reduce, reuse, and recycle.

These three Rs help us make less trash and save the Earth's things. Let us look at each one.

Key idea: The three Rs are reduce, reuse, and recycle.

Reduce: use less

To reduce means to use less of something. When we use less, we make less trash.

Here are ways to reduce:

• Turn off lights when you leave a room to use less electricity.
• Turn off the water while you brush your teeth.
• Take only as much food as you will eat.
• Use a lunchbox instead of new bags every day.

Key idea: To reduce is to use less, which makes less trash.

Reuse: use it again

To reuse means to use something again instead of throwing it away.

Here are ways to reuse:

• Use a water bottle you can fill up again and again.
• Turn an old jar into a pencil holder.
• Give clothes you have outgrown to a younger child.
• Draw on the back of used paper.

Key idea: To reuse is to use something again instead of throwing it away.

Recycle: make it into something new

To recycle means to turn old things into new things. Old items are collected, broken down, and made into brand new items.

Many things can be recycled:

• Paper can become new paper.
• Glass bottles can become new glass.
• Plastic bottles can become new bottles or even clothes.
• Cans can become new cans.

Many homes have a recycling bin. Putting the right things in it helps them get a new life.

Key idea: To recycle is to turn old things into new things.

Other ways to help the Earth

The three Rs are a great start. Here are more ways to help:

• Plant a tree or flowers. Plants clean the air and feed animals.
• Pick up litter you see, but only with a grown-up's help.
• Walk or bike for short trips instead of riding in a car.
• Take care of animals and the places where they live.

Key idea: Planting, cleaning up, and using less all help the Earth.

A safe home activity: a reuse project

Turn trash into treasure. Ask a grown-up to help.

1. Find a clean, empty container, like a can or a box.
2. Wash it and let it dry.
3. Decorate it with paper, crayons, or stickers.
4. Use it to hold pencils, toys, or treasures. You just reused it.

Key idea: With a little work, old things can become useful again.

Watch out for

• Thinking one kid is too small to help. Every small action adds up.
• Thinking all trash can be recycled. Check what your bin takes.
• Mixing up the three Rs. Reduce means use less, reuse means use again, recycle means make new.
• Forgetting to ask a grown-up before picking up litter.

Recap

• The Earth is our only home, and we can keep it clean.
• Pollution is anything that makes the land, air, or water unclean.
• Reduce means to use less.
• Reuse means to use something again.
• Recycle means to turn old things into new things.

Sources

1. National Geographic Kids, Save the Earth section, kids.nationalgeographic.com
2. Mystery Science, Caring for the Earth lessons, mysteryscience.com
3. PBS LearningMedia, Reduce Reuse Recycle resources, pbslearningmedia.org