Latent Heat

Definition

Latent heat is the energy released or absorbed by a substance during a phase change, such as the transition from solid to liquid or liquid to gas, without a change in temperature. It is a crucial concept in understanding the behavior of matter and energy transfer.

5 Must Know Facts For Your Next Test

1. Latent heat is the energy required to change the state of a substance without changing its temperature.
2. During a phase change, the temperature of the substance remains constant until the phase change is complete.
3. The amount of latent heat required for a phase change depends on the substance and the specific phase transition.
4. Latent heat of vaporization is the energy required to convert a liquid to a gas, while latent heat of fusion is the energy required to convert a solid to a liquid.
5. Latent heat plays a crucial role in regulating temperature and maintaining a stable environment, such as in the water cycle and the melting of ice.

Review Questions

• Explain how latent heat is involved in the process of boiling water.
  • When water is heated, it reaches its boiling point at 100°C. At this temperature, the latent heat of vaporization is absorbed by the water, causing it to transition from a liquid to a gas (steam) without a change in temperature. The energy required to break the intermolecular bonds and convert the liquid water into a gas is the latent heat of vaporization, which is a constant value for a given substance. This process of converting liquid water to water vapor at the boiling point is an important example of how latent heat is involved in phase changes.
• Describe the role of latent heat in the water cycle and its impact on temperature regulation.
  • The water cycle is a prime example of how latent heat influences temperature and climate. As water evaporates from the Earth's surface, it absorbs the latent heat of vaporization, which cools the surrounding environment. This absorbed heat is then released when the water vapor condenses back into liquid water droplets in the atmosphere, forming clouds. The release of latent heat during condensation warms the surrounding air, contributing to the formation of precipitation and the regulation of temperature on a global scale. The cyclic nature of evaporation and condensation, driven by the absorption and release of latent heat, is a key mechanism for maintaining a stable temperature on Earth.
• Analyze how the concept of latent heat can be used to explain the behavior of ice cubes melting in a glass of water.
  • When ice cubes are placed in a glass of water, the system will reach a state of thermal equilibrium as the ice and water interact. The ice cubes will begin to absorb heat from the surrounding water, causing them to melt. However, the temperature of the water-ice mixture will remain constant at 0°C until all the ice has fully melted. This is because the latent heat of fusion, the energy required to convert solid ice into liquid water, is being absorbed by the ice without increasing the temperature. Once all the ice has melted, the temperature of the water will then begin to rise as it continues to absorb heat. The constant temperature during the melting process is a direct result of the latent heat required to change the state of the water from solid to liquid.

Related terms

Specific Heat Capacity:

The amount of heat required to raise the temperature of a substance by one degree, which varies depending on the material.

Phase Change:

The transition between the three states of matter (solid, liquid, and gas) that occurs when a substance is heated or cooled.

Enthalpy:

The total energy of a thermodynamic system, including both the internal energy and the work done by or on the system.