Look at this cup. It looks empty. Is it really empty, or is something invisible inside it?
If air is something real, like water or a stone, what should we be able to show about it today?
We have two questions to test.
1. Does air take up space?
2. Does air have mass? Mass is the amount of matter in something. Matter is anything that takes up space, like water, wood or a stone. The more mass something has, the heavier it is, and we can compare mass fairly on a balance.
Talk with your partner. What do you predict for each question, and why?
Jot each short prediction on your Investigation Journal page now, before we test anything.
In your group, push an upturned cup straight down into the water with a small scrap of paper stuck in the top of the cup. Keep the cup level. Lift it out carefully and check the paper.
Then tip the cup slightly under the water and watch what happens.
Was your prediction right? What does this tell you about air?
Watch the beam balance carefully. Two balloons start the same. We will change only one thing: the air in one balloon.
Predict first with a clear show of hands. When the air leaves one balloon, will the balance: stay level, tip so the inflated side goes down, or tip so the empty side goes down?
On three, vote with one hand for your choice. Then watch what actually happens.
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