Publisher Summary This chapter presents the essentials, properties, and laws of thermodynamics. There are two types of thermodynamic properties: extensive and intensive. Extensive properties, such as mass and volume, depend on the total mass of the substance present. Intensive properties are independent of the amount of matter and it is possible to convert an extensive parameter to an intensive one. The Zeroth Law of Thermodynamics defines temperature. This law states that heat flows from one source to another only if there is a temperature difference between the two. Therefore, two systems are in thermal equilibrium if they are at the same temperature. The first law of thermodynamics establishes the principle of conservation of energy in thermodynamic systems. In thermodynamics, unlike in purely mechanical systems, transformation of energy takes place between different sources, such as chemical, mechanical, and electrical. All thermodynamic systems adhere to the principle of conservation of energy (the first law). The second law describes the restrictions to all such processes and is often called the Kelvin-Planck-Clausius Law.