A blacksmith is heating a piece of iron over a fire. He takes the hot metal and places it into cold water. Explain how heat would flow between the two substances.

Answer 1

When the blacksmith heats the iron over the fire, heat is transferred from the fire to the iron via conduction. As a result, the temperature of the iron increases. When the hot iron is placed into cold water, heat is now transferred from the iron to the water via convection. The water molecules near the iron get heated up as the heat flows from the iron to the water. These hot water molecules rise up, displacing the cooler water, and creating a current that carries the heat away from the iron. As the heat continues to flow from the iron to the water, the temperature of the iron decreases. This process is known as quenching and is commonly used in metalworking to rapidly cool and harden metals.