What you need:
An empty aluminium can, water, a bowl, tongs, a stove with a pan on it
What to do:
1. First, wash the soda can so it is free from any residues.
2. Fill the bowl with cold water, the colder the better. Ice water works too. Keep the bowl aside.
3. Put some water in the aluminium can. It can be about a tablespoon, just enough to cover the bottom of the can.
4. Light the stove and place the aluminium can on the pan.
5. Let the water inside the can heat and bubble up. When you see water vapour escaping from the can’s mouth, pick up the can using the tongs.
6. Quickly (and carefully!) invert the can and immerse it in the cold water.
What happens:
The can gets crushed!
Why?
Initially, the can is full of air and some water. When you heat it, the water boils and changes into gas, i.e. water vapour. This vapour pushes out the air that was originally inside the can as it expands.
When you turn the can upside down in the water, in effect, you close the mouth of the can. No more air can enter into it.
The cold water in the bowl causes the can to cool down, and the water vapour in it as well. As the water vapour cools, it contracts. So, it no longer occupies the entire space of the can. This contraction creates a low pressure zone inside the can. Ordinarily, air from outside would rush in and equalize this pressure, but thanks to the can being upside down in water, that cannot happen.
In this case, the pressure that the outside air exerts becomes so strong that it crushes the can! The contracting water vapour inside cannot exert enough pressure on the inside walls to help the can retain its shape.
Picture Credit : Google
