Convection

Convection is when heat energy is released, it rises as far as it can go. Eventually it cools. As cold air is denser (heavier) it sinks. When it gets hot again so it rises, and so on. this is known as a convection current. For example, a hot air balloon uses convection to get in the air. hot air is released, which floats up and helps the balloon float. cold air sinks, and gets heated up again by the engine. convection only happens in liquids and gases.