Atmospheric Pressure Experiment
The air in our atmosphere is constantly pushing on us and everything else.
There is even air pressure inside your body pressing outward. The air pressure inside your body counteracts the air pressure outside your body. This is how it is with most things on Earth. Comparable air pressure keeps things stable.
What happens when you alter the balance of air pressure? Test it with this atmospheric pressure experiment.
Soda Can Air Pressure Experiment
- Stove
- Frying pan
- 2 empty, 12 oz aluminum cans
- 2 bowls
- Water
- Ice cubes
- Tongs
- Eye protection
Procedure
1. Put just enough water in each aluminum can to cover the bottom of the can.
2. Fill each bowl half full of water and add several ice cubes to cool the water. The water needs to be very cold.
3. Stand the cans in a frying pan right side up.
4. Place the frying pan on the stove and turn the heat on “high”.
5. Watch for steam to come out of the top of the can. This might take a couple of minutes.
6. When a steady stream of steam comes out of the can, use the tongs to grab one can and place it upright in one bowl of ice water. Note what happens.
7. Use the tongs to grab the second can and place it upside down in the second bowl of ice water. Note what happens.
What Happened?
Before the experiment started, the air pressure inside the can and outside the can were the same. This stable air pressure allowed the can to keep its shape.
Steam, like air, is a gas, whereas water is a liquid. Gases take up more space than liquids, so we say they are less dense. When the water boils, the cans filled with steam and the air is pushed out.
This steam now exerted pressure on the inside of the cans, but it was the same as the air pressure pushing on the outside of the cans. This allowed the cans to keep their shape.
Placing the first can upright into the ice cold water changed the steam rapidly back to water. This caused air to rush back into the can keeping the air pressure in the can the same as the outside air pressure and allowing the can to keep its shape.
When the second can was placed upside down into the ice-cold water, the water blocked the opening to the can. This stops air from outside the can from getting inside the can. At the same time, the water vapor (steam) in the can begins to cool down rapidly resulting in a very small amount of water condensing inside of the can. This water takes up less space than steam. Since the opening of the can was under the water, air could not rush into the can to replace the steam like it could in the first can.
This creates a partial vacuum inside the second can, which means the space in the can has nothing in it. This means the pressure inside the can has dropped. Now, the air pressure outside the can is much higher than the pressure inside the can. The air pressing on the can from the outside is not meeting resistance from air in the can pressing out. Since there is no counter pressure from air inside the can, there is a partial vacuum inside of the can, and the can collapses.
Since there was little air pressure inside the can, there was not enough air pressure to counteract the air pressure outside the can. As a result, the outside air pressure crushed the can.
Side note: We cannot create a total vacuum. Vacuum means devoid of matter. The word comes from the Latin word (adjective) vacuus, which means vacant or void. Vacuus comes from the word vacare, which means empty. Here is a link of interest if your student wants to learn more about vacuums.
Try lifting the cooled can; a little bit of water is sucked up into the can. This is because the water pressure is pushing against the opening of the can, but only hard enough to fill a little of the can before the aluminum is crushed.
Other links of interest:
- Oxygen and fire experiment
- Take a peek at our journey through Apologia’s Anatomy and Physiology with our Science Saturday posts
- Check out these experiments in The Lab Report
- Why Apologia Science Is Great For Homeschool Co-ops
- Why Use Apologia Notebooking Journals
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