Lesson 7: Air Is Real
Air takes up space and has mass, even when it cannot be seen. Experiments with trapped and compressed air provide evidence of these properties and introduce air pressure.
Key Ideas
- Air is matter. It takes up space and has mass, even though we cannot see it.
- A balloon gets bigger as air fills it because the air needs room.
- Putting more air into a sealed container adds mass. Air is something, even when it looks like nothing is there.
- Air is made of gases. Gases spread out to fill the space available to them.
- Air pushes on us from all directions. Our bodies also push back, so ordinary air pressure does not crush us.
Vocabulary
- Matter: Anything that takes up space and has mass.
- Gas: A state of matter that spreads to fill all available space; air is a gas.
- Mass: How much matter an object contains.
- Air Pressure: The push of air on a surface. Air pushes in all directions.
Discussion Questions
- We know air has weight, but we do not feel it pressing down on us constantly. Why not?
- How would life on Earth be different if our atmosphere were ten times thicker?
- If air has mass and weight, why is it so much harder to measure the weight of air than the weight of a rock?
Supplies:
- Balance scale, bubbles, straw, cup of water, fan, balloon (2)
- A rigid, fixed-volume container and a suitable scale for a clearer air-mass comparison
- Alternative to balance scale: stick/dowel balanced on a string OR a hanger
- Bowl of water big enough for you to stick your hand in:
- Optional: a cup