Question

Q4. Define the terms latent heat of vaporization, latent heat of fusion.

Answer 1

Hmm..I am explaining in a very easy way. The latent term is used whenever there is a phase change process. Whether, a substance is converting from solid to liquid or liquid to gas, we use this term latent heat. So lets come to latent heat of vaporization. Here, vaporization indicates, a substance is converting from liquid to vapor.The literal meaning of latent is HIDDEN. So, it is a hidden heat. Why a word, LATENT is used here? Because, TEMPERATURE does not change in a phase change process. So you are supplying heat, but there is NO change in temperature. That is why, it is also called saturation temperature at a phase change point. Where does that heat go, then? It converts a matter from liquid to vapor without changing its temperatureSo, the amount of heat required to convert a substance from liquid to vapor at a given saturation temperature and pressure is called latent heat of vaporization. This quantity is a fixed quantity. It depends upon saturation temperature and pressure.At atmospheric pressure, the saturation temperature is 100 C. In order to convert 1 kg of water at saturation temperature to vapor, we need 2257 kJ of heat.Thus latent heat of vaporization of water at atmospheric pressure is 2257 kJ/kg.