We often think of the air around as "nothing." After all, when a cup is just filled with air, we call it empty. We can move around in air without it getting in the way. We can't see air!! This past week, rather than have me stand up and try to "prove" to students that air is made of matter, I put the ball in their court: The sixth graders were challenged to convince themselves and others that what seems like nothing is actually something. At this point, students already understood that anything made of matter has volume (takes up space) and mass (made of atoms, weighs something). But air?? They broke up into teams, looking to come up with the most different ways of demonstrating this counter-intuitive idea.
With lots of bottles, balloons, and straws, students collectively came up with dozens of ways to support the claim that air is made of matter. Some of our favorites included these two fun tricks:
1) Take a cup and stuff a paper towel inside. Then turn the cup upside down, straight down, until it is fully submerged in a bucket of water. Lift the cup straight up and notice that the paper towel is completely dry!
2) Put a balloon into the neck of the bottle so that the opening is covered. Try blowing the balloon up. It is impossible! (Unless you poke a hole in the bottle so that the air currently occupying the space can escape.) Try something similar with an inflated balloon. Put it on top of an "empty" bottle and the balloon won't deflate, even though it is open.
The best part of this learning was that students not only successfully convinced themselves that air is made of matter, but they also started asking deep questions about air pressure and compressibility - concepts we will return to during our study of the gas laws and weather.
