Properties of Pure Substances

pure substance

a substance that has a fixed chemical composition throughout (homogenous mixture)

is air a pure substance

air is a mixture of several gases, but it is considered to be a pure substance

phase equilibrium

two phases of a pure substrate can exist in equilibrium with a distinct boundary between them

compressed liquid

a substance that is not about to vaporize

saturated liquid

a liquid at Tsat and Psat that is about to vaporize

saturated vapor

a vapor at Tsat and Psat and is about to condense

saturated liquid-vapor mixture

the state at which the liquid and vapor phases coexist in equilibrium

superheated vapor

a vapor that is not about to condense

temperature during a phase change

constant at the saturation temperature

T-V diagram

saturation temperature

the temperature at which a pure substance changes phase at a given pressure

saturation pressure

the pressure at which a pure substance changes phase at a given temperature

latent heat

the amount of energy absorbed or released during a phase change process

property diagrams

equation of state

any equation that related the pressure, temperature, and specific volume of a substance

substances that cannot use the ideal gas equation

water and R134a

compressibility factor (Z)

a factor that accounts for the deviation of real gases from ideal-gas behavior at a given temp and pressure (PV = ZRT)

when do gases behave as an ideal gas

low densities: low pressure, high temperature