For instance, imagine heating 1 kg of water from a temperature 20 ° C 20 ° C to 21 ° C 21 ° C at a constant pressure of 1 atmosphere. Quasi-static and Non-quasi-static ProcessesĪ quasi-static process refers to an idealized or imagined process where the change in state is made infinitesimally slowly so that at each instant, the system can be assumed to be at a thermodynamic equilibrium with itself and with the environment. For analytical purposes in thermodynamics, it is helpful to divide up processes as either quasi-static or non-quasi-static, as we now explain. The manner in which a state of a system can change from an initial state to a final state is called a thermodynamic process. The change in a system can be fast or slow and large or small.

The state of a system can change as a result of its interaction with the environment. For example, the thermodynamic variables for a stretched rubber band are tension, length, temperature, and mass. Different types of systems are generally characterized by different sets of variables. For an ideal gas, these variables are pressure, volume, temperature, and the number of molecules or moles of the gas. The thermal behavior of a system is described in terms of thermodynamic variables.

Finally, with the interaction understood, we study the thermal behavior of the system with the help of the laws of thermodynamics. (We defined a system at the beginning of this chapter as anything whose properties are of interest to us it can be a single atom or the entire Earth.) Once our system is selected, we determine how the environment, or surroundings, interact with the system. We start by identifying the part of the universe we wish to study it is also known as our system.

In thermodynamics, we take a similar approach. In solving mechanics problems, we isolate the body under consideration, analyze the external forces acting on it, and then use Newton’s laws to predict its behavior. Calculate physical quantities, such as the heat transferred, work done, and internal energy change for isothermal, adiabatic, and cyclical thermodynamic processes.Distinguish between quasi-static and non-quasi-static processes.By the end of this section, you will be able to:

Interactive thermodynamics 3.2