Thermodynamics is the study of how energy is transferred and transformed. It is a branch of physics that deals with heat, work, and temperature, and how they are related. The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transformed from one form to another. The second law of thermodynamics states that heat can only flow from higher temperature to lower temperature, and that this flow will increase the entropy, or disorder, of a system. The third law of thermodynamics states that it is not possible to reach absolute zero, the coldest possible temperature, because as a system approaches absolute zero, its entropy approaches a constant minimum value. Thermodynamics is used in a wide range of fields, from engineering to chemistry to environmental science.