The First Law of Thermodynamics Work and heat are two ways of transfering energy between a system and the environment, causing the system’s energy to change. If the system as a whole . The first law of thermodynamics states that heat and work are equivalent energy forms and that the total energy stored in a thermodynamic system (per unit mass) can increase or decreased . There are four Laws of Thermodynamics, called the Zeroth, First, Second, and Third Laws because the Zeroth Law was developed la