Thermodynamics Is Two Laws

Isolated System. Energy and matter cannot cross the boundaries of an isolated system. Also the volume does not change the boundaries do not move. The total internal energy of an isolated sy stcm is constant. In reality, there is never complete isolation. This kind of idealization is common in thermodynamics. 

Semipermeable Membrane. A semipermeable membrane is a boundary that restricts the flow of some kinds of particle, while allowing others to cross. Dialysis is performed with semipermeable membranes. Biological membranes are semipermeable. 

Adiabatic Boundary. An adiabatic boundary allows no heat to flow between a system and its surroundings. Thermos bottles have adiabatic boundaries, more or less. Adiabatic walls permit you to measure work by prohibiting 

A phase is a homogeneous part of a system that is mechanically separable from the rest of the system. Homogeneous means that the pressure, temperature, and concentration are uniform, or continuous functions of position within a phase. In a simple system, a phase can be solid, liquid, gaseous, liquid crystalline, or other. 

These definitions, like much of thermodynamics, involve idealizations and approximations to reality. In this chapter and Chapter 8, we will focus on simple systems. 

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