The units of specific heat c are J/kg ? K, but the units of heat of fusion Lf or heat of vaporization Lv are simply J/kg. Why do the units of Lf and Lv not include a factor of (K)-1 to account for a temperature change?
Solution 11DQ We need to define both physical quantities first to understand the situation. Specific heat is defined as the amount of heat required to raise the temperature of unit 0 mass of a substance by 1 C. When the substance has a mass of m, change of temperature of T and Q is the heat given to the substance, specific heat sis given mathematically by the equation s = Q/mT . Therefore, in SI system, the unit of specific heat comes out to be J/kg.K. On the other hand, latent heat is the heat required to change the phase of a substance, like from solid to liquid or liquid to vapor at a constant temperature. If Q is the heat supplied to a mass mof a substance of latent heat L, then Q = mL or latent heat L = Q/m. Therefore, in SI system, the unit of latent heat will be J/kg. 1 The K term is not included because phase change happens at a constant temperature. So, no temperature term is included in the expression for heat unlike specific heat.