The first law of thermodynamics is a statement of the conservation of energy, which tells us that energy can be transferred from one form to another but never created or destroyed. It tells us how energy is related to work and heat, and it is typically stated through the equation:

This equation tells us that the differential change in energy (δE) is equal to the heat (δQ) that flows into the system minus the work (δW) the system does on its surroundings.