Enthalpy calculation with Cp

We can calculate the energy difference between two states of different temperature if we know the heat capacities.

When the pressure is constant, integration of ({ C }_{ p }) with respect to temperature gives the energy changes upon temperature change within a single phase. This energy change under constant pressure is called sensible heat. Since we can only calculate the energy difference between two states, the concept of a reference state where the zero enthalpy is assigned might be particularly useful. Then the enthalpy of a material at a certain state is not an absolute term but the enthalpy difference from the reference state. For compounds, heat of formation is assigned for the convenience in tabulation.