It's hard to imagine that air is matter in the same way that solids and liquids are matter. After all, matter is something that has volume (takes up space) and has mass (*can be weighed), and because air is invisible, it seems to have neither. In fact, for many thousands of years, people didn't even know that air existed. But air does take up space, even if we can't see it, and air has weight, even if we can't feel it -- and both of these properties can be observed and measured. The study of air as matter can be quite complex, but if broken down into a few basic facts, even kindergarten students can begin to understand the concept. This lesson focuses on the idea that air is actual "stuff" that occupies space and has mass that can be weighed. Students observe that air takes up space by "pouring" large bubbles of air underwater and by lifting objects with air-lifting bags. This also demonstrates that air exerts pressure, another important property of air.
*Weight is not the same as mass. Mass is the amount of material that makes up an object or substance (the number of molecules in a cup of water, for example). Because this is an abstract concept for young children, for our purposes, students consider mass in terms of weight. Weight is just the measurement of the force of gravity on mass. For example, lead has a large mass, so the gravitational pull on lead is strong. Air doesn't have much mass, so the gravitational pull is slight.
- Describe air as something that takes up space and has mass (as expressed by weight)
- Observe that air exerts pressure (presses on the things around it)
Grade Level: K-2
- One 90-minute block (can be divided into three or four sections)
- Air Is Matter Flash Image
- Density and Buoyancy: Pouring Air into Water QuickTime Video
- Lifting with Air QuickTime Video
- Lifting with Air handout (PDF)
- clear plastic tubs
- clear plastic cups
- clear plastic measuring cups
- bendable plastic drinking straws (or half-inch-diameter aquarium tubing)
- zipper-lock sandwich bags
- straight plastic drinking straws
- objects to lift with air-lift bags: juice boxes, shoes, small and large books
Before the Lesson
- Fill the clear plastic tubs with water, one tub per team of students.
- Make air-lifting bags using the instructions in the Lifting with Air (PDF) handout. Make one bag for each student. Note that this lesson uses sandwich bags instead of the gallon-sized bags featured in the handout.
1. Show the Air Is Matter still collage. Discuss the images and ask:
- In which of the images does flowing air make an object move?
- In which of the images is air used to fill an object?
- Can you think of another image, an action, or a sound that can be used to demonstrate that air is all around us?
- How would you convince somebody that air is all around us?
Next, go on an "air walk" to find evidence of air. Ask students to use their senses: see branches moving in the wind, feel a breeze on their skin, smell the aroma of food carried by the air to their nose, hear the rustle of leaves in the trees. Have a discussion with your students about air. Ask:
- How would you describe air?
- How does air behave?
- How do you know that you "found" air?
- Where else can air be found?
2. Play the Density and Buoyancy: Pouring Air into Water video. Using plastic cups and a tub of water, challenge students to pour air from one cup into another underwater, just as the kids on ZOOM did. Have them try using plastic measuring cups to measure how much air they can trap underwater. What happens when one-half cup of air is poured into a one-cup measure (and vice versa)?
Next, ask students to fill a cup with water and invert it in the tub of water, so that the cup contains no air, only water. Can they blow air from their lungs, through a bendable straw (or aquarium tubing), into the cup? Then ask:
- How much air can your lungs hold?
- How can you figure it out?
- Does air take up space?
3. Show the Lifting with Air video. Then have students lift small objects with their air-lift bags. What can they lift with air: a juice box? a shoe? a book? Challenge them to work in teams, using several bags to lift heavier objects. Discuss how one of the properties of air is that it presses on the things around it (exerts pressure).
4. Ask students if they know how much they weigh. Ask them how they know (they stand on a scale). Then ask:
- What would happen if you tried to measure air on a scale? How would you do it?
- Would it have weight, just like you do?
- Would it be heavy or light?
Check for Understanding
Ask students what they would say to someone who thinks that an inflated balloon is empty. Have them discuss this in pairs and report back to the class.