We remembered that the wind happened because of the sun and that warm air over the land rises and cold air over the water moves in to take its place.
We even remembered about Molecules (from last term - Mrs Hayman got happy tears) and how wind is there even though we can't see it. We thought air molecules must be really small.
We weren't sure if wind weighed anything. We thought it didn't BUT then we thought it has too because warn air must be lighter than cold air.
Our new Big Idea
Air is pulled down to the ground by gravity. As air is pulled down it presses on things. This is called air pressure.
Moving air does not press on objects as much as still air. It does not have as much pushing power.
Our Experiment
We had two containers the same height and placed a piece of paper across them. Mrs Hayman asked
"What will happen if we blow under the paper?" Everyone thought the paper would blow over and away.
We videoed Star of the Week Hazel.
We were amazed to see that the paper did not blow off in fact it pushed down!
Try it at home.
We decided it was because the still air was pressing down more than the air we were blowing (the moving air).
We tested this new thinking with a second experiment.
We hang blocks from a piece of string. We made sure they were the same height and 6 cm apart. We tried to blow them apart.
What we saw (but not as well as Mrs Hayman hoped) was that they acutally moved toward each other because of the still air pressing them.
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