Science Smarts: Under pressure

By Patty Rooks on November 26, 2022.

Often times when I watch the weather on the news, they are throwing out so many weather terms it is sometimes difficult to understand how it is all related to what is going to happen outside that day. One term I hear a great deal about is BAROMETRIC PRESSURE.

The forecaster will say the weather is changing today due to “a rise in barometric pressure.” Just what does this mean though? I think it is time we investigated this further. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Empty 2L soda bottle

– Water

– 3’x5″ recipe index card

– Pencil/pen

– Scissors

– Tape

– Clear glass cake pan

Procedure

1. Fill the empty soda bottle AND cake pan about ¾ full of water.

2. Invert the soda bottle into the cake pan. It will be useful to place your thumb over the mouth of the soda bottle until it is upside down and sitting perfectly still with the mouth under the water level in the cake pan.

3. Cut a couple of 1″x 5″ (approximately) strip out of the index card.

4. Tape this strip(s) on the soda bottle; place one end of the strip at the top of the bottle and tape it vertically in place all the way down the bottle (do not place any in the water though).

5. Using your pen/pencil place a mark on the index card where the water level is in the soda bottle.

6. Write the date here as well.

7. Repeat step(s) #5 and #6 for the next week.

8. What do you notice?

What is going on?

What I am about to tell you is a bit difficult to explain as we cannot see it. If we could, you would see that the weight of the air in the atmosphere is actually pressing down on the water in the cake pan. This keeps the water inside of the soda bottle and has a special term: air pressure. We do not even notice it, but the air pressure changes each and every day. When air pressure decreases, you will see a drop in your water level in the soda bottle. The weather person will then predict that there will be warmer, perhaps even wetter weather in the forecast!

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca

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