Air and Water Around Us

Look into a cup with no drink inside. You can see its bottom. Yet the cup is full of air, just like the room around you.

Find clues you can feel and hear

Clean air has no color. You can see through it, so looking alone will not show you where it is. Wave a sheet of paper near your cheek. The paper moves air, and you feel it brush your skin.

You can also hear air moving. Air rushing out of a balloon makes a hiss. Outside, you hear leaves rustle when air pushes them. Your eyes see the leaves move, even though they cannot see the air itself.

When you breathe in, air goes into your body. Your chest gets bigger. When you breathe out, some air leaves. Air is real stuff that can move into and out of places.

Watch air leave a bottle

Use a clear plastic bottle with no cap and a tub of water.

1. Look inside the bottle. It has no drink or toys inside.
2. Turn its opening toward the water. Keep the bottle tipped a little.
3. Push the opening under the water. Watch the opening closely.
4. Bubbles come out while water goes in.

Each bubble is a little pocket of air. The air was inside the bottle before you put it in the water. Water enters the space that the air leaves. The bubbles rise through the water and let their air out at the top.

You could explain your result like this: “I saw bubbles leave the bottle. The bottle had air inside it.” The bubbles are your clue; you did not have to see the air before the test.

Air spreads into gaps

Air is a gas. A gas spreads out to fill the space it can reach. Its tiny bits are much too small to see. Air fills gaps between objects and the space inside open cups, boxes, and bottles.

An “empty” lunch box has no lunch in it. That everyday word tells you what is missing, but air is still there. When you close the lid, you shut some of that air inside.

A book fills part of your backpack. Air fills space too, even though you can see through it. Tests can show you what happens when air is trapped.

Keep a paper towel dry underwater

Ask an adult to help with hands-on tests, especially balloons, cutting, and placing things outdoors.

1. Push a dry paper towel into the bottom of a clear plastic cup. It must stay in place.
2. Turn the cup upside down, with its opening facing down.
3. Push it straight down into a tub of water. Keep it upright.
4. Lift it straight up and feel the towel.

The towel stays dry. Air is trapped inside the cup. It takes up space, so water cannot fill that same space.

Now lower the cup again and tip it sideways underwater. Air escapes as bubbles. Water moves into the space it leaves, and the towel gets wet. Compare the two tries: tipping the cup gave the air a way out.

Make room for a balloon

A balloon grows when you blow air into it. The air needs space and pushes against the rubber. Let air out, and the balloon gets smaller.

Imagine a balloon inside a plastic bottle. Its neck is stretched over the bottle’s mouth. The bottle already holds air outside the balloon. That trapped air makes the balloon hard to blow up.

An adult can make a small hole in the bottle. Now air outside the balloon can leave through the hole. The balloon has room to grow. The hole lets the bottle’s air out; it does not put air into the balloon.

Squeeze air into less space

A syringe is a tube with a sliding part called a plunger. Use one with no needle. Pull the plunger back to let air in. Cover the tip tightly with your finger, then push the plunger gently.

The plunger moves inward. The same trapped air fits into a smaller space. You feel it push back. Let go of the plunger while keeping the tip covered, and it springs back outward.

Try a syringe full of water with its tip covered. The plunger hardly moves. This lets you compare the materials:

Squeezing air does not make it vanish.

A ribbon flutters outside your window. You feel a cool push on your face. These are clues that air is moving.

Spot the wind

Wind is moving air. Watch a flag, leaves, or clothes on a line. Moving air pushes them. You see what the wind does, even though the wind itself has no color.

A breeze is a gentle wind. It can make small leaves rustle. Strong wind can bend branches and push a trash can over. The same air is moving in both cases. Faster moving air pushes harder.

Compare the clues

Imagine watching the same flag on three days.

• On Monday, it hangs down with little movement.
• On Tuesday, it waves a little.
• On Wednesday, it stretches out and snaps in the wind.

Monday looks calm. Tuesday has a gentle wind. Wednesday has the strongest wind of the three. You compare what happens to the same flag, instead of guessing from a single sound.

A tree’s moving branches are another clue. The wind pushes the branches. The branches do not make the wind that is blowing through the street.

Make air move yourself

Wave a paper fan near a small strip of tissue. The fan moves air, and the tissue bends away. Move the fan slowly first, then faster. A stronger push of air moves the tissue more.

You can make moving air by blowing through your lips too. Put a little paper ball on a table. Blow from one side and watch which way it goes. Your breath pushes the ball away from you.

Follow the push

Moving air carries light things along with it. If wind blows toward a fence, loose leaves can move toward the fence. A pinwheel in that wind turns when the air pushes its blades.

Air is around you on a calm day too. A still flag does not mean the air has left. It means there is little moving air pushing the flag where you are watching.

Air can move a tiny paper boat or turn huge blades. It can also push against a falling parachute and slow it down.

Turn, sail, and fly

A pinwheel has slanted blades. Blow toward them, and the moving air makes them turn. A gentle blow makes the pinwheel turn slowly. A harder blow makes it turn faster.

Wind pushes the blades of a windmill too. People have used that turning motion to grind grain and pump water. A wind turbine uses turning blades to make electricity.

On a sailboat, wind pushes against the sail to move the boat. Wind also helps hold a kite up while you hold its string. In each case, air pushes on a surface.

Slow a falling toy

A parachute has a wide top called a canopy. Strings join it to a load, such as a small toy. As the toy falls, the open canopy meets the air. Air pushes up against it and slows the fall.

Earth still pulls the toy downward. A parachute makes the fall slower; it does not make the downward pull go away.

Compare two canopies fairly

Suppose you want to find out whether canopy size changes the fall.

1. Make one canopy 20 centimeters across and another 40 centimeters across. Use the same material and shape.
2. Attach the same small toy to each in turn. Keep the strings alike.
3. Drop each from the same height, letting go without a push.
4. Time each fall. Repeat each drop three times and record the times.

You changed one thing: canopy size. Keeping the toy, height, and way of dropping the same makes this a fair test. If you used a heavier toy as well, you would not know which change caused the result.

Read the result

In one test, the small canopy’s toy landed in about 1 second. The big canopy’s toy landed in about 2 seconds. The bigger canopy caught more air, so the air pushed up more and slowed its fall more.

Those times describe that test. Your own drops may take different times. Look across the repeated drops to see whether the bigger canopy usually takes longer. A twisted string or a folded canopy can spoil one try.

A large parachute does not fall faster just because it looks bigger. Its broad, open canopy gives the air more surface to push against.

Pour water into a bowl. It spreads across the bottom. Pour it into a narrow bottle, and it makes a tall column. Water can change its shape without changing its amount.

Watch it flow

Water is a liquid. You can pour it, and it runs or drips. On its own, water flows downhill, from a higher place to a lower place.

Tip one end of a tray up a little. A spoonful of water runs toward the lower end. You can follow its path with your eyes. Rain does the same thing when it runs down a slide or a sloping sidewalk.

People use this movement. A roof gutter guides rain away from a house. A funnel guides poured water through a small opening. Pipes carry water to and from sinks.

Look at the shape

Water takes the shape of the container holding it. A wide pan gives it room to spread sideways. A narrow vase holds it in a taller shape. When the water is still, its top is flat and level. Tip the container slightly, and the water moves to keep its top level.

Compare a rock with water:

Check the amount

Two cups of water can look very different in different containers.

1. Measure 2 cups of water.
2. Pour them into a tall, thin vase. Notice how high the water reaches.
3. Pour all that water into a wide pan. Its level is much lower.
4. Pour it back into the measuring cup. You still have 2 cups.

No water was added or spilled, so the amount stayed the same. The low water in the pan was spread over a wider space.

Compare without guessing

A higher water line does not always mean more water. To compare amounts in unlike containers, measure them or pour each into the same kind of cup.

For example, one spoonful in a skinny tube might reach higher than two spoonfuls in a bowl. Counting the spoonfuls tells you the bowl has more. The height alone cannot tell you that.

A wet sponge feels heavy with water. A plastic plate holds drops on top. Water goes into some materials and stays outside others.

Soak it up or keep it out

To absorb water means to soak it up. Water goes into a sponge, cotton cloth, or paper towel. The wet material still holds that water. Squeeze a wet sponge, and you see water drip out.

A waterproof material keeps water from passing through it. Water stays on plastic, glass, metal, or rubber. Tip the surface, and the water runs off.

These properties help you choose things for a job. A towel absorbs water from your hands. Rain boots keep water outside your socks.

Test before you choose

Compare small pieces of paper towel, plastic, aluminum foil, and cotton cloth.

1. Put each material on a tray.
2. Place one spoonful of water on each piece.
3. Wait one minute for each material.
4. Look for a wet patch inside the material or drops sitting on top.
5. Tip each piece gently and watch for water rolling off.

The same amount of water and the same waiting time help make the test fair. If you poured much more water on one piece, comparing the results would be harder.

A wet patch spreading through the paper shows that water soaked in. A drop rolling off the foil shows that water stayed outside it.

Look at the ground

Rain can soak into soil, grass-covered ground, and sand. Water enters sand quickly. Hard, packed soil lets it in more slowly, so puddles can last longer there.

After lots of rain, ground can already be full of water. More rain then runs off. On roofs and paved surfaces, much of the rain runs toward gutters and drains instead of soaking in.

Hardness does not tell the whole story

A soft rubber glove is waterproof. A hard, unglazed clay flowerpot can soak up water. You cannot choose an absorbent material just by checking whether it feels soft.

Suppose you need to dry a table and cover a picnic basket. Choose cloth for wiping up the water. Choose a waterproof cover for keeping rain off the basket. The two jobs need different properties.

An ice cube, a drink of water, and water vapor are all water. Their different forms explain many changes you see at home.

Freeze and melt

Ice is solid water. It keeps its shape when you move it from a tray to a plate. Liquid water flows and takes the plate’s shape.

Water freezes into ice when it gets cold enough, at 0 °C (32 °F) or colder. A freezer can turn water in an ice cube tray into solid cubes.

Ice melts when it gains warmth from warmer things around it. In a warm room, an ice cube warms to 0 °C (32 °F) and melts into liquid water. Freezing and melting can happen again and again. The material is still water.

Water takes up a little more space when it freezes. A full, closed bottle can bulge or crack in a freezer. Ice also weighs less than liquid water filling the same space. That is why ice cubes float in a drink.

Where does drying water go?

Water vapor is water as a gas. It mixes with the air, and you cannot see it. Evaporation is the change from liquid water to water vapor.

A wet shirt dries when water leaves the cloth and goes into the air. A puddle can dry in the same way. The water has changed form; it has not stopped being water.

Warmth and moving air help water evaporate faster. Picture two puddles that start the same size in the morning, one sunny and one shaded. By afternoon, the sunny puddle is gone and the shaded one remains. The sun warmed the first puddle, helping its water evaporate faster.

Look closely at drops

Water vapor can turn back into liquid drops on something cold. Drops on the outside of an ice-cold glass come from water in the air. They did not pass through the glass from the drink.

The white cloud above hot water is also tiny liquid drops. Water vapor itself is invisible. Keep away from boiling water and steam, which can burn you.

To watch melting without hot water, leave an ice cube on a plate in a warm room. Notice its edges shrinking and the puddle spreading. You are watching solid water become liquid water.

Turn on a faucet and water comes out. The faucet did not make that water. Its trip began somewhere in nature.

Name the source

A water source is a place where water is found or collected. Natural sources include rain, snow, rivers, streams, lakes, ponds, and oceans.

Some water is below your feet. Groundwater is water stored under the ground. A spring is a place where groundwater comes out naturally.

Built sources are made by people. A well reaches down to groundwater. A reservoir stores water; one kind is a lake made by damming a river. Rain barrels, tanks, water towers, pipes, and faucets help people collect, store, or get water.

Sort the place and the water

Ask, “Did nature make this place, or did people build it?”

Rain is natural even when it lands in a barrel people built. A well is built, but the groundwater it reaches is a natural source. You are sorting the source or structure, not changing what the water is.

Follow water to a faucet

Imagine a town that gets water from a lake.

1. The lake holds the water in nature.
2. People pump water to a treatment plant, where it is cleaned.
3. Pipes carry it through the town. A tower or tank may store it along the way.
4. A pipe brings it into a home. Opening the faucet lets water out.

Other towns start with river water or groundwater. Some homes use their own wells. A faucet is the end of a route, so different homes can have different routes.

Fresh water is precious

Most of Earth’s water is salty ocean water. Fresh water has very little salt. It comes from places such as rivers, lakes, and groundwater. Only a small part of Earth’s water is fresh water people can use.

Not every family has clean water from a faucet at home. Some people carry water from a shared well or another source far away. Having a safe supply close by leaves more time for school, work, and play.

Fresh water is different from safe drinking water. A river can hold fresh water and still contain harmful things. Salt water is not safe to drink either.

You need water and air every day. A seedling, a pet rabbit, and a whale need them too, but they get what they need in different ways.

Give a plant water where it needs it

Plants take in water through their roots. Water travels up the stem to the leaves. Their leaves also take in a gas from the air that helps them make food.

When a plant does not get enough water, it may wilt. Its leaves and stem droop. To water a plant, put water on the soil around its roots. Wetting a flower alone does not give the roots the water they need.

Water is a drink and a home

Animals get water by drinking and from food. A rabbit may drink from a bowl. A wild animal may drink from a pond. For fish and many other animals, water is also a place to live.

People and many animals breathe air. Fish use gills to take in oxygen mixed into the water. Oxygen is one of the gases in air too. Whales and dolphins live in water but come to the surface to breathe air.

Living in water does not mean every animal breathes the same way. A fish and a dolphin share a watery home, but get oxygen differently.

Follow water through your day

Water makes up more than half of your body. You lose some when you sweat, breathe out, and go to the bathroom. Drinking each day replaces water your body loses. You need more when it is hot or you are active.

People also use water to cook, wash, clean dishes, flush toilets, grow food, and put out fires. Swimming is a way to play in water.

Try grouping these water uses:

• Drinking at lunch helps your body.
• Washing a muddy shirt keeps clothing clean.
• Watering a vegetable garden helps food grow.
• Filling a pool makes a place to swim.

One home can use water for many jobs. Plants and animals need clean water too. Trash, oil, and soap in a pond can harm the animals living there.

Use air for more than breathing

Air fills balls and bike tires. Moving air dries clothes, pushes sails, and turns wind turbines. A clothesline uses the air’s movement to help water leave wet clothes. Water and air work together in this everyday job.

A faucet keeps running while someone looks for a towel. That water is going down the drain without being used. You can save it by turning the faucet off.

Save waste, keep what you need

To conserve water means to use water carefully and avoid waste. Keep drinking water and washing your hands. Your body needs both. Save the water that runs when it is not doing a useful job.

Clean fresh water is limited. Cleaning and pumping it takes work. Rivers, lakes, plants, and animals need water too.

At home, turn the faucet off while brushing or soaping your hands. Tell an adult about leaks. A small drip can continue all day and night. Full loads of dishes or laundry use water for more items at once. A short shower can use less than a full bath.

At school, close faucets fully and tell a teacher about a leak. Water the garden in the morning or evening, when less water evaporates. A rain barrel can collect water for plants.

Picture how much runs away

Imagine a faucet that gives about 6 liters in one minute. Left running for 2 minutes of brushing, it sends about 12 liters down the drain. You can picture that as six big 2-liter bottles.

Turning it off while brushing can bring the water used down to about 1 liter for wetting and rinsing. Compare the amounts:

That is about 11 liters saved for one brushing. Twice a day saves about 22 liters. Over a week, that adds up to about 154 liters. You do not have to stop brushing to save water.

Make a plan you can keep

1. Notice your water uses for one day. Draw a small mark each time you use water.
2. Circle times when water ran without being used.
3. Choose one or two changes you can make.
4. Write or draw your plan near the place you will use it.
5. Add a check mark each day you follow it.

A plan could say, “I turn off the faucet while I brush.” At the end of the week, count your check marks. Missing days show when you need a reminder.

You can also reuse water for a suitable job. Water left in your drinking bottle can go on a plant. A bottle kept cool in the fridge gives you a cold drink without running the faucet until the water cools.

A wrapper left beside a road can end up in a river. Water carries things as it flows, so keeping the land clean helps keep water clean too.

Follow a piece of litter

Imagine rain falling on a parking lot. It washes a candy wrapper into the gutter. The gutter carries it to a storm drain, an opening that collects rainwater from the street.

In many places, storm drains lead straight to a river, lake, or ocean. The rainwater is not cleaned along that route. A fish or turtle might try to eat the wrapper when it reaches the river.

Oil, dirt, and animal waste can travel with runoff too. Pollution can start far from the place where it harms a living thing.

Keep harmful things out

Water is polluted when harmful things get into it. These can include trash, paint, oil, cleaning chemicals, and too much soap. They can hurt plants and animals and make water unsafe for people.

Here are ways to help:

• Put trash in a trash can before rain can carry it away.
• Help keep parks and river edges free of litter.
• Pick up after pets with an adult’s help.
• Use the amount of soap you need, without extra squirts.
• Leave leftover paint, oil, medicine, and cleaning chemicals for adults to take to a special drop-off place.

A sink, toilet, or storm drain is not a place to pour those leftovers. Preventing pollution keeps harmful things from starting the trip.

Think about the next place

A river keeps flowing downstream. Something put into it can move to people, farms, and animals farther along. Floating trash does not disappear when it leaves your sight. Some travels on, and some sinks and stays on the bottom.

Picture two parks beside the same river. Trash from the first park can reach the second park. Putting trash away at the first park helps care for both places.

Clear does not always mean safe

Some germs and chemicals are too small to see. Water can look clear and still be polluted. Drink water an adult says is safe; do not drink from a river, lake, or puddle.

You cannot check drinking water by looking through a glass.

A bus engine makes exhaust, and a fire makes smoke. Both can put harmful things into air. You can help by choosing actions that reduce pollution.

Notice what dirties air

Air pollution includes harmful gases, smoke, and dust in the air. Cars, trucks, factories, chimneys, and fires can release them. Burning leaves or trash adds smoke too.

Dirty air can make eyes sting and make people cough. It can hurt plants and animals as well. Some pollution is visible as smoke or haze. Some harmful gases have no color or smell, so your eyes and nose cannot find them all.

Choose a useful action

Walking, biking, sharing rides, or taking a bus can mean fewer car trips. Adults can turn off car engines while waiting. Turning off unused lights and screens can also help. Some power plants burn fuel to make electricity, which puts pollution into the air.

Planting and caring for trees and other plants helps your surroundings. Avoid burning trash. When rain washes some dirt out of the air, that dirt can reach rivers and lakes. Protecting air helps protect water too.

Compare what air carries

You can use white cards with a thin layer of petroleum jelly to catch bits in the air. Have an adult place one near a busy road and one in a quiet garden. Leave them for the same three days. Then look at them with a magnifying glass.

A card with more dark specks caught more bits of dirt. The road card often has more. The cards show caught particles; harmful gases do not become visible specks. A clean-looking card cannot show you every kind of pollution.

Turn a problem into a plan

A class notices cars waiting outside school with engines running.

1. Name the problem: exhaust near children and plants.
2. Choose an action: make posters asking adults to turn engines off.
3. Count running engines during 10 minutes at pickup time.
4. Put up the posters with the school’s help.
5. Count again for 10 minutes at pickup time a week later.

In this class’s count, 12 running engines became 5. That means 7 fewer engines were making exhaust during the second count. Matching the place, time of day, and counting time helps the class compare.

Your class could choose water instead: notice litter near a drain, plan a cleanup, and check the same spot later. Give each person a job and choose a day to look again.