My 6th graders are currently studying the behaviors of liquids and gases. We are about to start density and just finished changes in gas pressure. To teach changes in gas pressure, we did a few mini activities as a class. First I gave each pair of students a balloon that was inflated a little bit. The students squeezed the air into different sections of the balloon and made observations about the air pressure.
After discussing the observations as a class, students used paint and Q-Tips (you could totally use markers or crayons) to paint 25 particles on the worksheet. They then painted 25 particles in each of the small cups. This is a good way for students to visualize the gas particles and why pressure increases.
We then talked about what would happen if a gas was heated and how the pressure would increase. Students made 25 dots in the second set of containers. They then drew a flame under the other container and showed the 25 dots in motion to show that pressure increased. Click on the picture below to download the PDF.