It expands and moves upward. Heavier, cold air replaces the warm air. Many homes are heated with convection currents. Hot air flows into the room from a vent near the floor. The hot air rises and warms the room.
Convection also causes the breeze at the seashore.
On a warm summer day, the land gets warmer than the ocean. During the afternoon, the land gives up some of its heat to the air. The hot air over the land rises. Cool air from the ocean moves in across the land. This cool air is a sea breeze.