12 Mar 2013

Air pressure on water

Hi you all!
Last week was the Water's Week in our school and we had different workshops working on that topic.
CM graders learnt that the air around us has weight, and it presses against everything it touches. That pressure is called atmospheric pressure, or air pressure. 

We started with  old and empty bottles, hammering a hole in a side of each bottle. Then we put a drinking straw through each hole.
Children discovered, when they filled them with water, and put the lids on, the water stoppped pouring through the straw, because air wasn't getting into the bottles, and couldn't pushing down the water. Otherwise, when they unscrewed the caps, the water was pouring ! It was fun and they enjoyed a lot. They talked about they had made a fountain with a tap.

If you're a kid who is trying to do this experiment, get an adult to help you make a hole in the bottle. I don't want to hurt yourself! You have to make the hole on a side of the bottle, close to the bottom.
Put a drinking straw through the hole you have just made it. Fill the bottle with water all the way to the half bottle. Screw on the cap. What's happen? Hey, there's no leak!

Slowly unscrew the cap and watch what happens. Are you ready for the water to come rushing out?


EXTRA INFORMATION: Atmospheric pressure is commonly measured with a barometer. In a barometer, a column of mercury in a glass tube rises or falls as the weight of the atmosphere changes. Meteorologists describe the atmospheric pressure by how high the mercury rises.

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