So today we're going to talk about the first law of thermodynamics, the second law of thermodynamics and the heat engine. So the first law of thermodynamics is an extension from the law of conservation of energy which states that energy cannot be created, it cannot be destroyed, it must be transformed from one form to another. Now, when we talk about the first law of thermodynamics, we basically, basically talk about closed systems. Now, aside from closed systems, they're open systems as well as isolated systems. Within a closed system, matter or mass is not allowed to exchange. The mass remains constant within the system.