Substance can be solid at low temperature, liquid at intermediate temperature, and gas at high temperature {phase, chemistry}|. States or phases have different relations between material volume, temperature, and potential energy.
free energy
Current phase has lowest free energy for temperature. Potential energy depends on distance between molecules. Entropy depends on molecule number and temperature.
phases: solid
Solid phase has lowest volume and smallest potential energy, because average distance between molecules is smallest. Solids have low chemical potential. Low temperature makes material solid, because decrease in potential energy is higher than decrease in entropy. Solid phase has most order, because it has patterned crystal structure and temperature is lowest. Solid phase has least randomness and lowest entropy. Solids can have several crystal forms and so different solid phases.
phases: gas
Gas phase has highest volume and greatest potential energy, because average distance between molecules is greatest. Gases have high chemical potential. High temperature makes material gas, because increase in entropy is higher than increase in potential energy. Gas phase has least order, because all molecules are independent, with no physical structure, and temperature is highest. Gas phase has greatest randomness and highest entropy.
phases: liquid
Compared to solid, liquid phase has more volume and more potential energy, as distance between molecules becomes more. Intermediate temperature makes material liquid, because entropy change is similar to potential energy change. Liquid phase has less order than solid phase, because crystal structure breaks down into fluid structure, and temperature is more.
factors
Temperature, pressure, phase number, and substance amounts, concentrations, and pressures affect chemical systems.
factors: independence
Some factors relate to others, and some are independent. Available phases are independent, because substances can go to all phases.
factors: temperature
Temperature can freely vary, must be the same throughout system, and does not depend on other factors.
factors: pressure
Pressure can freely vary, must be the same throughout system, and does not depend on other factors.
factors: substances
Number of independent components is number of substances minus one. Because total percentage must be 100%, because sum of mole fractions must equal one, one substance's percentage is dependent.
factors: number
With no equilibria in system, number of independent factors is (c - 1) * p + 2, where c is component number, and p is phase number.
factors: equilibrium
Substance amounts in two phases in contact at phase boundary typically are in equilibrium. Chemical potentials of both phases must be equal. Number of equilibria is c * (p - 1), where c is component number, and p is phase number.
factors: degrees of freedom
Factor number and equilibria number determine how many factors {degrees of freedom, equilibrium} can freely change in chemical systems. Degrees of freedom equal free-variable number v minus equilibria number e {phase rule, components}: v - e. Degrees of freedom total: c - p + 2 = 1 + 1 + (c - 1) * p - c * (p - 1), where c is component number, and p is phase number.
factors: equilibrium and ions
If chemical systems have ions, electrical neutrality requires adding one more equilibrium to chemical system.
factors: equilibrium and initial state
Knowing chemical-system initial state fixes one more factor and adds one more equilibrium.
factors: equilibrium and field
If force field is present in chemical system, it adds one more phase to chemical system.
factors: equilibrium and phases
Two immiscible substances can make two heterogeneous phases, even if both are liquids, because they have boundary. Both components are in equilibrium. Heterogeneous phase is mixture and has several components, several phases, and several equilibria.
Two miscible substances can combine to make only one homogeneous phase, with no boundary, because they mix and so are not in equilibrium. Homogeneous phase counts as one component and one phase.
phase change
Physical systems tend to go to lowest potential energy and greatest entropy. Electrical forces push or pull atoms and change potential energy to kinetic energy. Friction opposes electrical forces, so kinetic energy tends to become heat. Physical systems tend toward most randomness and lowest physical order and so greatest entropy. Number of molecules freed from order relates to average random kinetic energy and so temperature.
phase change: free energy
Total available energy is free energy and is energy from order breakdown plus potential energy. Physical systems tend to go to lowest free energy. Lowest free energy is optimum between lowering potential energy and raising entropy.
phase change: temperature
System has same average random translational kinetic energy throughout. Temperature stays constant during phase change from gas to liquid, or liquid to solid, because all heat energy removed is potential energy, which kept molecules apart, not kinetic energy. Temperature stays constant during phase change from solid to liquid or from liquid to gas, because added kinetic energy from heat becomes potential energy that makes molecules farther apart.
Physical Sciences>Chemistry>Inorganic>Phase
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Date Modified: 2022.0224