enthalpy

(noun)

the total amount of energy in a system, including both the internal energy and the energy needed to displace its environment

Related Terms

Examples of enthalpy in the following topics:

  • Phases of Matter

    • shows the different states of matter and how they can change from one to another as a function of enthalpy and pressure and temperature changes.
    • A solid can change to a liquid with an enthalpy increase.
    • A liquid can change into a gas when it hits its boiling point or can even enter a plasma state if the enthalpy is increased enough.
    • When the enthalpy is lowered, a liquid can transform into a solid through freezing.
    • This figure illustrates the relationship between the enthalpy of a system and the state of matter that the system is in.

  • Calorimetry

    • Dividing the energy change by how many grams (or moles) of A were present gives its enthalpy change of reaction.
    • A constant-pressure calorimeter measures the change in enthalpy of a reaction occurring in solution during which the atmospheric pressure remains constant.
    • where Cp is the specific heat at constant pressure, ΔH is the enthalpy of the solution, ΔT is the change in temperature, W is the mass of the solute, and M is the molecular mass of the solute.
    • Constant-pressure calorimetry is used in determining the changes in enthalpy occurring in solution.
    • Under these conditions the change in enthalpy equals the heat (Q=ΔH).

  • Relativistic Shocks

    • Here $w$ is the enthalpy per unit volume whereas in previous sections it denoted the enthalpy per unit mass, $w_\mathrm{mass}=w_\mathrm{volume} V$.
    • The first term cancels in the previous equation, leaving the middle term which equals twice the enthalpy per unit mass.

  • Ideal Fluids

    • where $w=(\epsilon + P)/\rho$ is the heat function (enthalpy) per unit mass of the fluid.

  • Heat Capacity

    • With the enthalpy of the system given by
    • Explain the enthalpy in a system with constant volume and pressure

  • Detonation Waves

    • The lower curve $a$ is the shock adiabat without the chemical changes and $a'$ is the detonation abiabat which uses the functional form of the enthalpy in the burnt gas.

  • Radiative Shocks

    • However, the enthalpy of an isothermal gas is given by

  • Non-relativistic Shocks

    • We can use the definition of the enthalpy to eliminate it from the equations
    • Because the specific enthalpy $(p_1,V_1)$ i$P$s a function of $P$ and $V$$w = \gamma/(\gamma - 1) p V$, the eighteenth equation in this section defines a curve.

  • Specific Heat for an Ideal Gas at Constant Pressure and Volume

  • B.12 Chapter 12

    • where $w$ is the enthalpy per unit mass.