Now when we talk about the transfer of energy, remember that there are only two types of transfer of energy work and heat. Now heat can be subdivided into three categories convection, conduction and radiation. When we talk about chemical work, we talk about this type of work pressure times change in volume. And when pressure remains constant, we use this equation. When pressure isn't constant, we use calculus and integrate from the initial to the final. Now this law can be summarized in this equation.