Crushing the can
The empty soda can having a lower internal air pressure, will collapse inwards due to the higher water pressure outside the can.
Air molecules have a certain mass and when these molecules collide with a surface, pressure is felt on that surface. The molecules in the air contain kinetic energy and are always moving. The moving molecules are always colliding with one another or onto other surfaces creating the phenomenon that we call pressure.
Let us say we have a sealed container containing air. If we increase the amount of air molecules in the container, the number of air molecules colliding with the inner walls of the container will increase and so will the air pressure. If the number of air molecules inside the container is reduced, the air molecules colliding with the inner walls of the container will also reduce along with the air pressure inside the container.
Another method of varying the air pressure inside the container is temperature. Increasing the temperature of the container will cause the molecules inside the container to have a greater amount of kinetic energy. This will make the molecules collide more frequently amongst themselves and on the inner surface of the container causing the air pressure inside to be greater. Cooling down the container will reduce the kinetic energy and also lessen the collisions within the inner walls of the container, causing the air pressure to fall.
1. Perform the experiment under adult supervision.
2. Be careful, and request assistance if necessary, when handling the stove, and when removing the hot soda can from the stove and placing it in the cold water.