|Air pressure is all around us. We live in a sea of air, but it’s hard to see its effects. Here’s an activity that will help you see the power of air pressure.
You will need:
an empty aluminum soda can
- a hot plate
- a plastic dishpan or other large container
- a pot holder or pair of tongs
- a ruler
- a calculator
- safety goggles
Be sure to wear safety goggles. Pour a little cold water into the can. Pour cold water into the dishpan until it is about 3/4 full.
Place the soda can with water on the hot plate and heat until steam is coming out the top of the can. Pick up the can at its base, using the pot holder or tongs, and quickly invert it into the cold water contained in the dishpan. If nothing seems to occur, put a little water back into the can and try again.
Draw a sketch and write a short description of what you did and what happened. Answer the following questions:
What happened when the can was inverted into the cold water?
- What caused the can to crush? Draw a diagram of what you think happened inside and outside the can before, during, and after it was immersed in water.
- Why didn’t the empty soda can crush before it was heated?
- Would the same thing have happened if you put the can in right side up? Predict, then try it out!
Hint: At sea level, average atmospheric pressure supports a column of mercury 760 mm high in a mercury barometer. This average sea level pressure is called 760 torr in honor of Torricelli, and is also called one atmosphere of pressure. So 760 mm of mercury = 760 torr. How might atmospheric pressure affect the can?