Basic Concepts in Thermodynamics

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Equilibrium. Equilibrium is a condition where bodies or spaces are at rest, and there are no active thermodynamic changes, changes in heat or pressure occurring. The concept of equilibrium can apply to particles as small as single cells, or as large as the planets in the universe. All could be in equilibrium where there is no act of transfer of heat or pressure occurring. Balance is a key concept in considering equilibrium. By definition, equilibrium is a state in which opposing forces or influences are balanced. In our own experiences, we referred to losing our equilibrium if we trip over a rock and temporarily lose balance. We recover equilibrium when we regain balance and can stand or walk again. In the physical world, if various pressures are balanced and changes are minimized, we would consider the environment to be in equilibrium. Forces may still exist, but cancel each other out, so the net force is zero and the object remains in equilibrium. Some objects may even be moving with relatively few opposing forces. This is referred to as dynamic equilibrium. A car for example, traveling at a constant speed would be in dynamic equilibrium, but accelerating or applying the brakes eliminates equilibrium since we're making one force override another. As heat energy is introduced, the body may change its thermodynamic state, which is the specific set of conditions that make up an environment. Changes in the conditions, also called variables, cause changes to the thermodynamic state. Some of the variables affecting the thermodynamic state could include temperature, pressure, volume, or force. Water changes its thermodynamic state when we put a pan on a hot stove and the temperature rises. The water eventually boils, and some of it turns into steam. The process of changing states is called the thermodynamic process. If a body is an equilibrium, then one or more variables change, a thermodynamic process is triggered. Scientists have defined four types of thermodynamic processes. In an isothermal process, temperature remains constant, but other variables change. Adiabatic refers to the heat content or quantity of matter remaining constant. Isochoric identifies a process where the volume of the system remains constant, and Isobaric refers to pressure of the system remaining constant.