Enthalpy

Enthalpy is a property of a system also referred to as the heat of that system. Heat and temperature are not the same, but they are related by a simple formula. This can be utilized in calorimetry, where the change in temperature is used to calculate the change in enthalpy associated with a chemical reaction. Enthalpy is denoted with the symbol H, and it is measured in joules, J, which is a measure of energy.

Enthalpy, H, is defined as

H = U + pV

Where U is the internal energy of the system, p is the pressure and V is the volume. pV is the same as the work, w. You may recall from the first law of thermodynamics that the change in energy of a system, U, is given by the sum of the heat and the work applied to that system.

Read about the correlation between heat and energy.

Read about enthalpies of formation and reaction

Read about exothermic and endothermic reactions