The amount of heat per unit mass that is transferred in a phase change is called
The correct answer and explanation is:
The amount of heat per unit mass transferred during a phase change is called latent heat. This term refers to the heat required to change the phase of a substance without changing its temperature. The process occurs when a substance transitions from one phase to another, such as from a solid to a liquid or from a liquid to a gas.
Latent heat is essential because it reflects the energy required to overcome the molecular forces within a substance. During a phase change, the temperature remains constant, as all the energy supplied goes into breaking the bonds or forces between the molecules, rather than increasing the temperature of the substance.
There are two primary types of latent heat:
- Latent heat of fusion: This is the amount of heat required to change a unit mass of a substance from solid to liquid at its melting point, or vice versa. An example is the heat required to melt ice into water.
- Latent heat of vaporization: This is the amount of heat required to change a unit mass of a substance from liquid to gas at its boiling point, or vice versa. A common example is the heat required to turn water into steam.
In both cases, the temperature of the substance does not increase during the phase change because the energy is used for the rearrangement of the molecules rather than speeding them up (which would increase temperature). The latent heat depends on the substance, with different materials requiring different amounts of heat for their phase changes. This principle is fundamental in many natural and industrial processes, including boiling, melting, and freezing.
The concept of latent heat helps explain why substances like water can absorb or release large amounts of energy while remaining at a constant temperature during phase changes. This plays a crucial role in weather systems, cooking, refrigeration, and other fields that involve heat transfer.