FOCUS: The air we breathe is part of the Earth’s atmosphere, a layer of gases that surrounds the planet, protecting us from harmful radiation and keeping us warm. Although air is invisible, we’ll discover that it takes up space, exerts pressure and has weight, can be heated, cooled, and compressed, and always seeks to equalize its pressure. It is important to understand our atmosphere, because without air, animals and plants could not survive.
Objective: To begin to explore and ask questions about air.
Give each small group of children an empty bag, and ask, “What’s in the bag?” Now ask children to twist the neck of the bag shut with a twist-tie, and have them feel it again. Is the bag really empty?
Materials: Plastic bag and twist tie, one for each group.
STATIONS: The following activities are best done in small groups and could be set up in stations: Paper Flip, Air Trap, Pump Action, Rise and Fall, and Diving Dropper.
Objective: To use a model to see that air has weight and exerts pressure on a surface.
Spread out a section of newspaper on a table so that it is as flat as possible and so that one edge is even with the edge of the table. Carefully slide a wooden paint stick under the paper so that about a third of the handle sticks out. Ask the children if a lot of strength would be needed to flip the paper into the air with the paint stick. Now have a child give one quick rap with the side of the hand against the wooden paint stick. Does the paper fly up into the air? (Usually not.) Could the child feel a weight pressing against the stick? What happens when you press on the stick slowly so that air gets under the paper? (It is easier to flip.) Try lifting the paper with the stick to feel its weight. Is the paper heavy? Try folding it into quarters. Now you have made it smaller, but it is still the same weight. Have the children stand back and have an adult hit the stick gently to flip the paper. (Caution: the stick flies out more easily now.) When it’s folded, the paper is easy to flip, but when it is spread out, it is hard to move. What is holding it down? (Air.) Because air is a gas, it pushes in all directions. When you slowly press the stick, air gets under the paper and pushes against it from underneath, with a pressure equal to the air pressing from above – so you only feel the weight of the paper itself.
For older students: Explain that a one-inch column of air extending from sea level to the farthest edges of the atmosphere exerts a pressure of 14.7 pounds, or about a ton of pressure on every square foot of ground. Ask for ideas about how they could calculate the weight of air pressing on the newspaper. Have students measure the area of the paper (length x width in inches), then multiply the area by air pressure at sea level (14.7 lb/in²). This is how many pounds of pressure the air is exerting on the spread-out newspaper.
Materials: several sections of newspaper, wooden paint sticks; optional for older children: rulers or yard sticks, calculators, pencils, paper.
Objective: To use a model to see that air takes up space and can be compressed.
Ahead of time, fill a small aquarium or basin with water. Now hold up a clear glass or plastic drinking cup. Stuff a tissue into the glass so that it stays in the bottom, even when you hold the glass upside down. Carefully press the glass downwards into the aquarium until it is submerged. Ask the children to look carefully and notice whether the water goes up into the inverted cup. (A tiny bit.) Lift the cup straight out of the water, keeping it inverted, and pull out the tissue. Is it wet or dry? (Dry.) Why doesn’t the water get inside? (Air in the glass is blocking the way.)
Now have the children take turns pushing the cup of air into the water to feel the resistance, and watch to see if it fills with water. Why can water go in a little way? (Because it squeezes the air into a smaller space.) Can air be compressed? (A little bit.) What happens when you tip the cup? (Air bubbles float to the surface and the cup fills up with a little more water.) Which way do the air bubbles move? (Up – air is lighter than water.)
*For an extra challenge, trying pushing in a second cup, filled with water. Try “pouring” air from the first cup into the second, while keeping both underwater. What happens?
Materials: small aquarium or basin filled with water, clear glass or plastic drinking cups, tissues or paper napkins.
UPPER GRADES CHALLENGE: Diving Dropper (Grades 5-6)
Objective: Use a model to see how air, a gas, can be compressed, while water, a liquid, cannot.
Fill a liter-sized plastic water bottle almost to the top with water. Add enough water to a glass eye dropper until it just floats when placed in the water bottle. (Adjust this first using a basin of water.) Put the cap on tightly and squeeze the bottle. What happens to the dropper? (The dropper sinks to the bottom.) What happens when you stop squeezing? (The dropper floats back up.) Now repeat, observing closely what happens to the water level in the bottle and in the dropper as you squeeze the bottle. (The water level in the bottle goes up and in the dropper too – more water goes into it.)
Ask for ideas about why this might happen. Why does the dropper sink? (The water that enters makes it heavier.) Why does the water go into the dropper? (Air can be compressed but water cannot. When you squeeze the bottle, there is less room inside it, so the water goes up in the bottle. It also pushes into the dropper and squeezes that air into a smaller space. When the pressure is released, the air expands back to its original volume, the water goes out of the dropper, and the dropper floats up again).
Materials: liter-sized plastic water bottle with cap, glass eye dropper (pipettes will probably not work), basin, water.
Objective: To use a model to discover how air that is compressed exerts pressure in all directions.
*Please keep everyone behind the pump and aim the bottle away from people in the classroom. The tops can fly quite a distance and can hurt if they hit someone.
Poke a hole with a thumbtack into the side of a plastic milk container. Close the milk bottle with its plastic (non-screw) cap. Now carefully insert the needle of an air pump. (Have extra needles on hand in case one breaks.) An adult should hold the bottle, aiming it in a safe direction, while children take turns pumping air into it. What happens to the sides of the container as more air is added? (They begin to puff out.) Why does the top eventually pop off? (As more air is added to the bottle, it pushes outward in all directions, eventually popping off the top.)
Try larger and smaller containers. Have the children make predictions about the number of pumps needed to pop off the top for different sizes of containers. Are more pumps needed for larger or for smaller containers? Count pumps to see if their predictions are correct.
Materials: air pump for soccer balls with extra needles, a variety of plastic bottles of different sizes with non-screw caps; optional: safety goggles.
RISE AND FALL
Objective: To investigate what happens to air when it is heated or cooled.
What happens to air when you heat it up or cool it down? Hold up an empty plastic water bottle and ask the children what’s inside. (Air.) Fit a small, uninflated balloon over the neck of the bottle. Have a child place the bottle into a container of hot water. Ask where the air came from that went into the balloon. (From inside the bottle.) Now have the children take turns placing the bottle into a container of ice water and then into a container of hot water. What happens to air when you heat it? (Expands, spreads out.) When you cool it down? (Shrinks, sinks back into the bottle.)
Materials: one-pint plastic water bottle, small three- to five-inch balloons, container of hot water, container of ice water.
Objective: To model the behavior of molecules in a solid, liquid, and gas.
Everything in the world is made of molecules, tiny particles too small to see even with a microscope. Explain that the group is going to act out what it’s like to be a molecule in a solid, like a rock; in a liquid, like water; and in a gas, like air. In a solid the molecules are touching and bonded together. Have the children form a close group, touching elbows and crowding together. They can’t detach from neighbors and move around, but they do vibrate (jiggle) in place. In a liquid the molecules don’t stick tightly to neighbors and can slide past each other. Have children move around in slow motion, no longer touching elbows. A liquid fills its container, and flows downhill if it tilts. In a gas, the molecules are widely spaced and can move around in all directions, including upwards. They don’t touch unless they bump into each other or into something else. When they bump into an object or a wall, they turn and go a different way. Have everyone move around freely, reversing directions when they touch something. Continue until everyone has spread out to fill the room. When they are warm they move faster; when they cool off they have less energy and get closer together, though not as close as in a liquid. What would happen if a door was opened? (Some of the gas would go out.)
PUPPET SHOW “Half Full or Half Empty?”
Objective: To learn how air is important to living things.
Perform the puppet show, or have a group of children perform it for the class. Afterward, ask questions to review the key details and vocabulary in the story. Why is air needed by animals? (For energy.) By plants? (To make leaves, stems, etc.) Holding up each puppet, review how each one gets air. What is the part of air that people and animals especially need to breathe? (Oxygen.)
Materials: puppets, script, stage, props.
Objective: To model some additional ways that air is important to living things.
Besides needing air to breathe, animals and plants make use of air for different purposes. Divide the class into small groups and have each team practice a short skit to demonstrate a way that air is important to their animal or plant. Give each group one of the following scenarios:
Airy Act 1: Rabbits and hares keep warm when the cold wind blows in winter because they have fur, which traps warm air close to their bodies. (Keeping warm.)
Airy Act 2: Insects buzz their wings to fly through the air. Birds flap their wings, using air to fly and chase flying insects. (Flying.)
Airy Act 3: Crickets rub their wings together to make sound waves that are carried by the air. Sounds help them to find each other. (Carrying sound.)
Airy Act 4: Skunks lift their tails and give a puff of scent when frightened. Air carries the smell and scares off their enemies. (Carrying odors.)
Airy Act 5: Trees make seeds with wings that spin. The air carries their seeds to places where they can grow. (Carrying seeds.)
After each skit, ask the rest of the class to identify the function of air that was demonstrated.
Materials: Airy Acts skit cards, props including furry clothing, craft feathers, combs, skunk tail cut-outs, helicopter seed cut-outs; optional: insect costume such as bug-eye glasses, antennae.
DESIGN CHALLENGE: BUILD A PARACHUTE
Objective: To design and build a parachute to slow an object falling to the ground.
Have students work in pairs or small groups to design and build a parachute that will slow the fall of a pinecone, large paper clip, or other small object. The main criterion for success is that the parachute must slow the fall of the cone, compared to a free-falling cone of the same size and weight. The main constraints are the materials for constructing the parachute. Provide various materials such as paper plates, coffee filters, paper cups, yarn or string, etc. Include small balls of clay or different-sized clips to hold the strings together. This helps to quickly modify the weight to get the parachute to fly better. Launch the parachutes from a play structure outside, in a stairwell, or from a ladder. Test each design by dropping a pinecone (or whatever kind of object is being used) with and without a parachute at the same time. Have children compare the different designs. Which were most effective in slowing the pinecone’s descent? Have them work together to modify their parachutes and then retest them. How might air pressure be important in how a parachute functions? (The parachute compresses the air underneath it so it pushes upwards and outwards, which partly counteracts the force of gravity pulling the parachute towards the ground.)
Materials: variety of materials for construction such as coffee filters, plastic bags, fabric squares, string, yarn, thread, etc.; similar-sized pinecones, large paper clips or other small objects; scissors, tape; optional: timer, journals or clipboards and paper, pencils.
OUTSIDE AIR OBSERVATIONS
Objective: To look outside for evidence of air in motion.
Take children outside in small groups and visit different locations on the school grounds. Have them list or tell about examples they notice of air in motion. What can they see that is caused by moving air? What sounds can they hear that are caused by moving air? What can they do so they can feel the air moving? Afterwards, share findings with other groups.
Materials: optional: clipboards, pencils, paper.
JOURNAL ACTIVITY and CLOSING THOUGHTS
Objective: To reflect on favorite activities on windy days, or on their parachute designs.
Have children draw a picture or write about a fun thing to do outside on a windy day. Have them share their journal entries in small groups.
For older children: Have children draw their parachute designs in their journals, listing materials and discussing how they might improve the design. Give their parachute design a name and share these in small groups.
Materials: journals or clipboards and paper, pencils.
EGG IN A BOTTLE*
Objective: To observe that air seeks to equalize its pressure.
*Caution – this activity requires the use of matches or a lighter, and a small fire is made inside the bottle. The smoke may set off smoke detectors.
Ahead of time, prepare some hard-boiled eggs by boiling them for ten minutes, cooling and peeling them. Explain that you are going to see if you can use air pressure to push an egg into a glass milk bottle. Place a glass milk bottle on a table and place the egg over the opening of the bottle to show that it is too big to fall in. Now remove the egg and set aside. Make a few accordion pleats in a two-inch square of paper. Light one corner of the paper with a lighter or match and drop it into the bottle. Quickly place the hard-boiled egg over the opening of the bottle and watch the egg until it drops in. What did the children notice when you lit the paper? (Smoke came out of the bottle, and therefore some air left too.) What made the egg go in? Have the children try to work out an explanation from what they have learned about heating air, and air pressure. (When the air expands from the heat of the fire, it rushes out of the bottle. Placing the egg in the opening blocks air from returning and leaves the air pressure lower inside the bottle than outside. The air in the room pushes against the egg until it drops in, when the room air can now refill the void in the bottle and equalize its pressure with that outside the bottle.)
Challenge the children to suggest a way to get the egg back out of the bottle without breaking it up. (Hold the bottle upside down so the egg settles into the neck. Slip a straw that has been flattened at the end along one side of the egg and blow into the bottle. Or slide the needle of the pump next to the egg. Blow or pump air into the bottle until the egg comes out. Be sure to have a basin at the ready to catch the egg.)
Tips: Try using a small or medium egg. Wetting the egg slightly helps it slip in without breaking. It is also easier to get a smaller egg out. If the milk bottle is quite cold before the burning paper is dropped in, the egg drops in more quickly. Smaller pint containers get quicker and more consistently successful results.
Materials: quart- or pint-sized glass milk bottles, hard-boiled eggs, water, matches or lighter, small two-inch squares of paper, air pump, basin; optional: bowl of hot water, bowl of ice water.
A STEP BEYOND:
Jumping Jacks: Have the children count how many breaths they take in one minute. Then have them do ten to twenty jumping jacks. Now have them count their breaths again. Is there a difference? Why?
How Much Air?: Fill a gallon jug with water and invert carefully (so that it loses as little water as possible) into a dish basin containing a few inches of water. Place one end of a flexible tube into the neck of the jug (keeping it below the water surface) and keep the other end above water. Have each child insert a straw into the outside end of the tube, take a deep breath, and blow into the straw. How much air do our lungs hold? How many children does it take to fill the jug with air?