Question

A tin can sinks when it is heated with a lid closed and then poured cold cold water in it. Why?

Answer 1

Why collapsing of tin take place when we heat it and then put cold water over it? When the tin is heated, the air within and water molecules expand. As the volume expands, so does the tin container up to a limit. It is possible that a small amount of air and water vapours escape if the tin is not 100% airtight. Subsequent cooling reduces the molecules volume thus creating a vacuum. The outside air pressure being greater than internal pressure and assuming that mini holes that existed before heating have self healed during heating, outside air can not come in to fill the void space. Therefore, the thin tin container collapses till pressure within and without balance.