"A state function, function of state, or point function for a thermodynamic system is a mathematical function relating several state variables or state quantities (that describe equilibrium states of a system) that depend only on the current equilibrium thermodynamic state of the system."
A property of a system that is independent of the path used to reach that state. Examples include internal energy, enthalpy, and entropy.
Internal Energy: Internal energy is the sum of all the kinetic and potential energies of the particles that make up a system. It is a state function that describes the energy of a system at any particular moment.
Enthalpy: Enthalpy is the sum of the internal energy of a system and the energy that is transferred from the surroundings. It is a state function that describes the total energy of a system.
Entropy: Entropy is a measure of the disorder or randomness of a system. It is a state function that describes the degree of randomness in a system and is closely related to the number of possible arrangements a system of particles can take on.
Gibbs Free Energy: Gibbs free energy is a thermodynamic state function that describes the energy available for use during a chemical reaction or physical process at constant temperature and pressure. It is often used to predict whether a reaction will be spontaneous or non-spontaneous.
Phase Equilibria: Phase equilibria is the study of the equilibrium between different phases of matter, such as liquids, gases, and solids, and how they relate to changes in temperature or pressure.
Chemical Equilibrium: Chemical equilibrium is a state in which the rate of a chemical reaction is equal to the rate of the reverse reaction, resulting in no net change in the concentrations of the reactants and products.
Thermodynamic Laws: The three laws of thermodynamics, which include the conservation of energy, the increase in entropy, and the unattainability of absolute zero, are fundamental principles that govern the behavior of closed and open systems.
Standard States: Standard states are reference states used as a baseline for measuring thermodynamic properties, such as pressure, temperature, enthalpy, and entropy.
Heat Capacity: Heat capacity is a physical property of matter that describes the amount of heat required to raise the temperature of a substance by one degree Celsius or Kelvin. It is a measure of the substance's ability to store thermal energy.
Calorimetry: Calorimetry is the process of measuring the heat absorbed or released during a chemical reaction or physical process by measuring changes in temperature. It is often used to determine enthalpy changes and heat capacities.
Internal Energy (U): The sum of all the kinetic and potential energies of the molecules in a system.
Enthalpy (H): The heat content of a system at constant pressure.
Free Energy (G): The energy available to do work in a system at constant temperature and pressure.
Entropy (S): A measure of the disorder or randomness of a system.
Helmholtz Energy (A): The energy available to do work in a system at constant volume and temperature.
Gibbs Energy (G): The energy available to do work in a system at constant temperature and pressure.
Heat Capacity (C): The amount of heat required to raise the temperature of a system by one degree.
Joule's Law Constant (J): A measure of the ratio of the internal energy of a gas to its temperature.
Internal Pressure (π): The pressure exerted by the molecules in a system on each other.
Chemical Potential (μ): The energy required to add one mole of a substance to a system at constant temperature and pressure.
Volume (V): The amount of space occupied by a system.
Temperature (T): A measure of the average kinetic energy of the molecules in a system.
Pressure (P): The force per unit area exerted by the molecules in a system on its container.
Density (ρ): The mass per unit volume of a system.
"A state variable is typically a state function so the determination of other state variable values at an equilibrium state also determines the value of the state variable as the state function at that state."
"In this law, one state variable (e.g., pressure, volume, temperature, or the amount of substance in a gaseous equilibrium system) is a function of other state variables, so is regarded as a state function."
"A state function describes equilibrium states of a system, thus also describing the type of system."
"Internal energy, enthalpy, and entropy are examples of state quantities or state functions because they quantitatively describe an equilibrium state of a thermodynamic system, regardless of how the system has arrived in that state. In contrast, mechanical work and heat are process quantities or path functions because their values depend on a specific 'transition' (or 'path') between two equilibrium states that a system has taken to reach the final equilibrium state."
"Heat (in certain discrete amounts) can describe a state function such as enthalpy, but in general, does not truly describe the system unless it is defined as the state function of a certain system, and thus enthalpy is described by an amount of heat."
"Internal energy, enthalpy, and entropy are examples of state quantities or state functions."
"A state function describes equilibrium states of a system."
"A state function for a thermodynamic system is a mathematical function... that depend only on the current equilibrium thermodynamic state of the system (e.g. gas, liquid, solid, crystal, or emulsion), not the path which the system has taken to reach that state."
"A state function describes equilibrium states of a system, thus also describing the type of system."
"A state function could also describe the number of a certain type of atoms or molecules in a gaseous, liquid, or solid form in a heterogeneous or homogeneous mixture, or the amount of energy required to create such a system or change the system into a different equilibrium state."
"Internal energy, enthalpy, and entropy are examples of state quantities or state functions because they quantitatively describe an equilibrium state of a thermodynamic system, regardless of how the system has arrived in that state."
"In contrast, mechanical work and heat are process quantities or path functions because their values depend on a specific 'transition' (or 'path') between two equilibrium states that a system has taken to reach the final equilibrium state."
"Heat (in certain discrete amounts) can describe a state function such as enthalpy."
"This can also apply to entropy when heat is compared to temperature. The description breaks down for quantities exhibiting hysteresis."
"A state variable is typically a state function."
"A state function describes equilibrium states of a system, thus also describing the type of system."
"A state variable is typically a state function so the determination of other state variable values at an equilibrium state also determines the value of the state variable as the state function at that state."
"One state variable (e.g., pressure, volume, temperature, or the amount of substance in a gaseous equilibrium system) is a function of other state variables, so is regarded as a state function."
"A state function could also describe the number of a certain type of atoms or molecules in a gaseous, liquid, or solid form in a heterogeneous or homogeneous mixture, or the amount of energy required to create such a system or change the system into a different equilibrium state."