I’ve got that David Bowie and Queen song stuck in my head this week… “Under pressure… Pushing down on me…”
Okay, now that we had a musical segway, onto pressure. We began, as we usually do, by copying the definition of pressure into our science journals. Then, to demonstrate right on the notebook, we each picked a colored pencil and experimented with different pressures. You can see Mushroom at it below. We also just tried putting pressure on different things and talking about the things that put pressure on us.
Then, we headed outside to hammer in some nails. First, we tried hammering them in upside down to show how a sharper point can be influenced by pressure.
When we came inside, I showed them this video from Youtube where a teacher demonstrates laying on a bed of nails and having a cement block broken over another bed of nails on his chest. The kids were as fascinated and appalled as the students in the video. We used it to talk about how the pressure was spread out. BalletBoy and Mushroom have actually lain on a bed of nails before at the Maryland Science Center, where they have a machine that allows the nails to rise slowly to ensure that the pressure gets distributed evenly.
Our next series of experiments came mostly from this website. I’ve used some of their experiments before for other topics. We tried the experiment with the lemon diver, where you make a little slice of lemon dive down by changing the air pressure, however, we couldn’t get a balloon to fit over the lid of the jar properly. Doing the marshmallow faces also fizzled out. I’m pretty sure the seal on the jar was airtight. However, I think I might have needed to buy the really nice marshmallows to make it work. I think the cheap ones weren’t puffy (and therefore air-filled) enough.
However, we did a number of variations on this experiment where you keep things dry by using air pressure under the water. Even though it was simple, the kids were enthralled that you could hold air under the water. Also successful was when I gave each kid a little bowl and a piece of cardboard. When you fill the cup with water, put the cardboard on it and make a snug seal, you can flip it over and remove your hand. The pressure will keep the cardboard in place.
To finish off our experiments with water, we put some holes into a plastic bottle and watched how the greater pressure at the bottom pushes the water out farther. This was a good jumping off point to talk about how the changing air pressure can make our ears pop and how if you dive to the bottom of a deep swimming pool you can really feel the pressure.
To finish us off, I let the kids all try out the air pressure gauge for the tires on the car. One tire was a little low, so we stopped and filled it on the way to take our science pals home. I love it when science and errands come together!