You can catch us on Channel 12’s Arizona Midday on Monday, April 18th from 12:30-1:30 as we demonstrate the crushing power of air pressure on live television!
Every year around Earth Day, my daughter and I try to come up with ways to help protect the environment, with a big focus on the Three R’s, Reduce, Reuse and Recycle! We’ve held Earth Day Parades, toured recycling facilities, and have built a model town for Katie’s toys out of recycled materials! This year, we wanted to spend Earth Day thinking about our atmosphere, and exploring some of the more interactive properties of it. Namely…. air pressure!
Every day, we sort our trash into recycling. We go through a lot of aluminum cans in our house, as we all enjoy sparkling water. I crush these cans every day, and one day I got to thinking, what if I could crush these cans, not with my hands, but with AIR? Thus, our Earth Day experiments were born!
Before we get started, I want to take a look at air, and how in the world we could use it to crush a can of all things! Well, air is made of “stuff”, of tiny particles of matter! This matter consists of mostly Nitrogen (78%), Oxygen (21%), Argon (0.93%), Carbon Dioxide (.039%), and other trace gasses. These elements, just like any other kinds of matter, have weight that presses down on us at all times. Indeed, the atmosphere weighs about 15 lbs, per square inch! With all of the weight of the entire atmosphere, from the ground to the reaches of outer space pressing down on us all the time, that equals to about 1,000 pounds of pressure all day, all the time!
So, why don’t we feel all of that pressure?
Well, the atmosphere is pressing on us from all sides! It’s pushing down, up, in, out, it’s everywhere! It’s also pushing out from within our bodies. Our stomach, ears, lungs.. we have a ton of pressure pressing out from within us as well, which equalizes all of that air. You can feel changes in pressure when you go in an airplane, or drive up or down a windy mountain road. Our ears will pop to create an equilibrium, which helps keeping us from being negatively affected by all that pressure.
Well, if we were to take some of the air OUT of the equation, the rest of it would immediately crush what was left! We can see this in effect with our aluminum can crusher!
CANS UNDER PRESSURE
Empty soda can
Stove top or camp stove
1 tbsp of water
Put on your safety goggles, then fill your bowl with ice water and set it aside.
Fill your empty soda can with about 1 tablespoon of water. Using oven mitts and tongs, put your soda can on your stove or burner, and turn the heat up to medium-high.
Heat your can until the water starts boiling. You’ll know this is happening when you start to see steam escaping from the top of your can. You might also hear little popping sounds as air bubbles begin to pop inside.
Using your tongs, quickly and carefully pick up the can, and immediately turn it over and plunge it, top side down, into the ice water!
When you flipped your can over into your ice water bath, you should have seen the crushing power of air pressure at work! When you boiled the water inside the can, it caused the air inside to heat up and expand. You saw the water vapor escaping the can, well that was along with the air inside!
When you put the can in the ice water bath, it immediately cooled and condensed the small amount of air remaining inside. It condensed into just a few little drops of water! With almost no air left in the can, it created it a vacuum. Now, there was no pressure pressing OUT from the can, and only air pressure pressing IN from all sides, outside of the can! Thus, the crushing power of air pressure can be seen, right in your kitchen!
Now, one thing you might have noticed if you picked your cans up out of the ice water, was that water was pouring out of them. You might think water was sucked into the cans when they crushed, but there’s actually another reason for it, and yet again, it has to do with air pressure! Here’s another demonstration you can do at home to see how it works!
MAKING WATER RISE WITH AIR PRESSURE!
Tall narrow jar (glass, vase, or flask!)
Lighter (adult supervision!)
Food coloring (optional)
Have an adult help you light your candle. Drip a few drops of candle wax onto the center of your plate. Quickly blow out the candle and stick it in the wax.
Pour a bit of water on the plate, making sure that the base of the candle is covered in water. Then, have an adult light the candle.
Quickly and carefully cover your candle with the jar! Make sure the bottom of the jar is submerged in the water, and not pressing on the candle.
When you light the candle, it heats up the air immediately surrounding it. Cover it with the jar, and that air heats up a lot faster! As it heats up, the air expands, and some of it escapes. This, combined with the burning of oxygen, causes there to be less air inside the jar than outside of it. This creates a vacuum, and the air pressure outside of the jar, pushes the water into the jar to make up for the difference, creating an equilibrium!
Experimenting with air pressure is a fantastic way to be able to see some of the things that remain unseen in our world. By removing the air from an object, you can see the crushing weight that exists all the time! Thankfully our bodies are adapted to exist with these pressures, but when pressures change, our bodies need to be able to adjust in order to function! This is why airplanes have cabin pressure, and why astronauts have pressurized suits when they go to space! Space is a vacuum, and as we’ve seen with the vacuums we’ve created in our kitchen, this can have some crushing impacts if the pressure isn’t equalized.
You can experiment with different ways to see air pressure too! Try using different temperatures in your ice water bath, or heating up your water inside the can to lower temperatures. At what temperature will the water boil, causing some of the air to escape the can? With the rising water demonstration, will the number of candles used affect how much the water rises? Does the temperature of the water change how it rises? Are there any other (non-flammable!) materials you can use instead of water?
There is an incredible world of science waiting to be explored all around us. Sometimes you can’t see all there is to know! But, while you can’t see it with your eyes, perhaps you can study the effects of it as you make changes to the atmosphere around you. Seeing the impacts of something, is how scientists study things that we can’t easily see, such as seismic activity in the Earth’s core, or gravitational waves out in space! In this way, you’re participating in evidence gathering, while “seeing the unseen!” You can think of many ways to gather evidence of the scientific principles at work around us, and as always..