How does latent heat play a role in changes of state?

Latent heat is the energy absorbed or released during a change of state, without changing the substance's temperature.

Latent heat plays a crucial role in changes of state, also known as phase transitions, such as melting, freezing, boiling, and condensing. These changes of state occur when a substance absorbs or releases energy, specifically in the form of heat. However, during these processes, the temperature of the substance does not change, despite the heat transfer. This is where the concept of latent heat comes in.

The term 'latent' means hidden. So, latent heat refers to the 'hidden' heat that is either absorbed or released during a phase transition. This heat is 'hidden' because it does not cause a change in temperature. Instead, it changes the state of the substance. For example, when ice melts to become water, it absorbs latent heat from the surroundings but its temperature remains constant at 0°C until all the ice has melted. This absorbed heat is used to break the bonds between the ice molecules, causing a change in state from solid to liquid.

Similarly, when water boils to become steam, it absorbs latent heat from the surroundings. The temperature of the water remains constant at 100°C until all the water has boiled. The absorbed heat is used to break the bonds between the water molecules, causing a change in state from liquid to gas.

On the other hand, when a substance changes state from gas to liquid (condensation) or from liquid to solid (freezing), it releases latent heat to the surroundings. Again, the temperature remains constant during these processes. The released heat is the energy that was previously used to break the molecular bonds in the substance.

In summary, latent heat is a fundamental concept in understanding changes of state. It is the 'hidden' energy that is absorbed or released during phase transitions, causing a substance to change its state without changing its temperature.