the effects of motion, viscosity, fluid shear, capillarity, anisotropic stress, and external force fiels are ABSENT
has uniform thermodynamic properties throughout is said to be homogeneous
a homogeneous and invariable chemical composition and may exist in more than on phase. Include, water, mixture of liquid and water vapor, CO2, N2, mixture of gases, etc.
molecules are not fixed positions relative to each other, can rotate and translate freely. The intermolecular forces are weaker relative to solids.
atoms or molecules arranged in three-dimensional patterns
molecules are far apart from each other and molecular order is nonexistent
(subcooled liquid) - not about to vaporize
about to vaporize, at temperature when liquid beings to boil
the amount of energy absorbed or released during phase-change process
Temperature is greater than the saturated temperature for the given pressure, and vapor is NOT about to condense
temperature of chamber is constant until saturation pressure is reached (3.17 kPa at 25 C), then saturation conditions are mainated at progressively lower pressures and correspond to lower temperatures, until desired temp is reached
T-V phase diagram
property diagram for phase-change process
when the saturated liquid and saturated vapor state are identical, phase change is indistinguishable. At temp/pressure above this point, the phase changes are no longer discrete
pressure and temperature of a substance exist in three phases of equilibrium
at low pressure (below triple-point), solids evaporate before melting
energy transfer of force acting through a distnace. Depends on path of process.
Work over a unit of time (kJ/s, or kW)
Moving Boundary work
W > 0: work done by the system (expansion)
W < 0: work done on the system (compression)
Wb = ∫ P dV
Area under PV curve is boundary work
net work during a cycle, difference btwn work done by and on the system.
Depends on path and end states.
Point function: ∫ dP = P - P = 0
path functions: ∫dW = ∫ PdV ¹ 0
U total energy (kinetic and potential) in a system
Includes chemical bonds, intermolecular attractions, electrons, etc.
amount of energy required to increase the temperature of a substance by 1o C (ext. prop)