The Air up there: Build your own barometer to measure atmospheric pressure

Science With Stevie

(WIVB)–Air is all around us and the atmosphere is essential for life on earth. Different weather patterns are influenced by the pressure of the air.

We are going to talk about how we can measure air pressure, in this week’s episode of Science with Stevie.

One way we can measure and predict the weather is by using an instrument called a Barometer. Barometers are used for detecting the changes in atmospheric pressure. You can build a barometer with just a few simple materials that you may have around your home. You will need a glass, a balloon, a spool, straw, pencil, toothpick, and a marked index card with an “H” for high pressure at the top, and an “L” for low pressure at the bottom. 

Cut the balloon and stretch it over the top of the glass, and the straw will be glued onto the balloon, with the toothpick extending off the edge of the straw. Think of the air as a fluid and the changes in pressure help to move it.

While we can see water being poured in and out of a jar, we cannot see air. So, we can use a balloon to see how the air moves pertaining to pressure. Let’s look at the jar with a balloon, straw, and toothpick on top. When the air pressure inside of the jar and outside of the jar are the same, the toothpick will be level so make sure to put a tick mark on your index card. 

Low pressure outside of the jar will pull the balloon up so the pressure inside matches the pressure outside. When air rises, it cools, condenses, and forms clouds which therefore leads to precipitation. The opposite is true with high pressure.

As the pressure rises outside of the jar, it will begin to push down on the balloon. This is because the high-pressure air is denser. As the air inside matches the air pressure outside, it shrinks in size and pulls the balloon down. Overall, this can help us determine the air pressure and therefore we can make predictions about the weather. 

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