1. The Pushing Air Trick
We learned that even though we don't feel the air around us all the time, it's there and pushes on everything. We feel it push against us when it moves as wind, but this experiment showed us that it pushes in all directions, even up.
B filled a plastic cup all the way up to the brim with water, then covered it with a plastic-coated postcard and pushed the card down. He kept one hand flat on top of the postcard and held the bottom of the cup with the other hand. Then, over the sink, he turned the cup upside down and removed the hand holding the postcard. He laughed with glee when the postcard stayed under the cup, exclaiming. "I'm doing a magic trick!" The air under the postcard was pushing up enough to keep it in place.
To measure how much and when air pushes more than other times, we made our own barometer with an empty mason jar, balloon, straw, rubber band, tape and cardboard (cut from a cereal box in the recycle bin).
I cut the "neck" off the balloon, stretched it over the mouth of the mason jar and B secured it with a rubber band. I cut one tip of the straw at an angle to form a point and B taped the other end of the straw to the middle of the balloon. Then B taped a piece of cardboard to the jar. Using a pencil, B made a mark on the cardboard where the straw pointed and checked it several times this week for movement.
We've had a lot of rain and thunderstorms come and go and the straw has mostly been pointing down. Yesterday morning, B woke me up, pouncing on the bed in excitement, "Mama! Our barometer is finally pointing up! We're out of low pressure and into high pressure, finally!" It was a clear, sunny morning. When the air pressure outside the jar became high, it pushed down on the balloon, causing the pointed tip of the straw to rise. When the air pressure outside the jar was low, the air in the jar pushed up and the pointed end of the straw lowered.
3. Homemade Thermometer
B had been asking exactly how a mercury thermometer works. His Nana has one at her house but we only have a digital ear thermometer. So this experiment came at the right time.
B took a bottle out of the recycle bin, pulled the label off and filled it with water. I added some blue food coloring to the water. With modeling clay, I sealed the top of the bottle with a straw sticking out of it. B put the bottle in a glass bowl and I poured simmering water into the bowl (see photo, left).
As the blue water inside the bottle heated up from the simmering water outside of it, the blue water expanded and rose up the straw (see picture, below). As the water cooled, it contracted and the straw emptied back to the way it was at the beginning of the experiment.
As the air around a thermometer warms up, the liquid in it rises. As the air around a thermometer cools, the liquid inside lowers.
|Water inside our thermometer rising from the heated water outside of it.|