Day 29, Ethan-5th Grade Student

Oh, the pressure!  By Ethan

In Challenge today we studied atmospheric pressure.  We also learned about how molecules act when they’re cold and when they’re hot.  It’s easy to remember because when molecules are cooler they get closer together, like when you’re cold you pull sweaters or blankets closer to you.  When you’re hot, you want to spread out and you don’t want anything near you, like when molecules are warmer they spread out.

We made barometers with a plastic cup, a balloon which was stretched over the top of the cup, and a coffee stirrer glued to the middle of the balloon stretched over the cup. When the pressure was lower the balloon went up, and when it is higher the balloon would go down. We proved this by taking the barometers outside.  The air pressure outside was lower than inside the classroom so we got to see the balloon on the top of the barometer bulge up a little.  It was almost immediate.

Did you know that there is 15 pounds of air pressure pushing on every square inch of you?  We also did an experiment with a water bottle that had a hole in it. The bottle was full of water, and there was no leaking because there was 15 pounds pushing on the bottle. This is called air pressure.  When we loosened the top and allowed more air in the water squirted out, but quit when we tightened the lid again.  Then we emptied the water into an electric kettle to heat the water up. 

After the water was heated, we poured the warm water back into a different water bottle without a hole in it. With that water we warmed the air inside the water bottle. When we put the cap back on, the water bottle started to crinkle because the air pressure was lower inside the water bottle than the air around it.  That’s because when we heated the air inside it expanded and pushed some of the air out.   We took off the cap and the water bottle slowly returned to normal size for the warm air was moving out, and the cooler air was moving in to make the air pressure equal.