A pan is on the stove ready to boil some peas. The water inside it is heated by convection, and as you watch you can see a convection current occur. Explain what convection is and why convection currents happen.

Part A) Convection occurs in liquids. In this process, more energetic particles move from warmer regions to cooler ones and take their energy with them.

A convection current happens because when a fluid is heated it expands. This decreases its density causing it to rise upwards. As it moves away from the heat source it becomes cooler and is pushed aside by the warmer liquid below it. Because it is cooler, it has a higher density and it sinks down to the bottom again.

Part B) Convection cannot happen in a solid because the atoms inside the solid are held together by stronger intermolecular forces that prevent the atoms from moving very far.