The amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure at its melting point.
Explanation
Latent heat is the amount of heat energy absorbed or released by a substance during a change in its physical state (phase transition) without any change in temperature. The term "latent" implies hidden, as the heat supplied does not raise the temperature but is used to overcome the forces of attraction between the particles.
Detailed Analysis:
- The amount of heat required to raise the temperature of 1 kg of solid by 1°C. is Incorrect. The amount of heat required to raise the temperature of 1 kg of a substance by 1°C is defined as Specific Heat Capacity. This process involves a change in kinetic energy and temperature, not a phase change.
- The amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure at its melting point. is Correct. The Latent Heat of Fusion is specifically defined as the amount of heat energy required to change 1 kg of a solid into a liquid at atmospheric pressure at its melting point. During this process, the temperature remains constant until the entire solid has melted.
- The heat energy released when a liquid solidifies. is Incorrect. This refers to the heat released during solidification or freezing. While the magnitude of energy involved is the same as the latent heat of fusion, the term "fusion" specifically denotes the melting process (solid to liquid).
- The heat energy required to convert liquid into vapour at its boiling point. is Incorrect. The heat energy required to convert a liquid into vapour at its boiling point is defined as the Latent Heat of Vaporization.
Key Takeaway:
Latent Heat of Fusion is associated with the phase transition from solid to liquid at a constant temperature (melting point), whereas Latent Heat of Vaporization is associated with the transition from liquid to gas at a constant temperature (boiling point).