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  2. Thermodynamic equations - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_equations

    Entropy cannot be measured directly. The change in entropy with respect to pressure at a constant temperature is the same as the negative change in specific volume with respect to temperature at a constant pressure, for a simple compressible system. Maxwell relations in thermodynamics are often used to derive thermodynamic relations. [2]

  3. Energy conversion efficiency - Wikipedia

    en.wikipedia.org/wiki/Energy_conversion_efficiency

    The energy efficiency of a process involving chemical change may be expressed relative to these theoretical minima or maxima.The difference between the change of enthalpy and the change of Gibbs energy of a chemical transformation at a particular temperature indicates the heat input required or the heat removal (cooling) required to maintain ...

  4. Mass–energy equivalence - Wikipedia

    en.wikipedia.org/wiki/Mass–energy_equivalence

    The initial value of the energy is arbitrary, as only the change in energy can be measured and so the m 0 c 2 term is ignored in classical physics. While the higher-order terms become important at higher speeds, the Newtonian equation is a highly accurate low-speed approximation; adding in the third term yields:

  5. Thermochemical equation - Wikipedia

    en.wikipedia.org/wiki/Thermochemical_equation

    In thermochemistry, a thermochemical equation is a balanced chemical equation that represents the energy changes from a system to its surroundings. One such equation involves the enthalpy change, which is denoted with Δ H {\displaystyle \Delta H} In variable form, a thermochemical equation would appear similar to the following:

  6. Gibbs–Helmholtz equation - Wikipedia

    en.wikipedia.org/wiki/Gibbs–Helmholtz_equation

    The definition of the Gibbs function is = + where H is the enthalpy defined by: = +. Taking differentials of each definition to find dH and dG, then using the fundamental thermodynamic relation (always true for reversible or irreversible processes): = where S is the entropy, V is volume, (minus sign due to reversibility, in which dU = 0: work other than pressure-volume may be done and is equal ...

  7. Calorimeter - Wikipedia

    en.wikipedia.org/wiki/Calorimeter

    The temperature change in the water is then accurately measured with a thermometer. This reading, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts), is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and ...

  8. Carnot's theorem (thermodynamics) - Wikipedia

    en.wikipedia.org/wiki/Carnot's_theorem...

    A reversible heat engine with a low efficiency delivers more heat (energy) to the hot reservoir for a given amount of work (energy) to this engine when it is being driven as a heat pump. All these mean that heat can transfer from cold to hot places without external work, and such a heat transfer is impossible by the second law of thermodynamics .

  9. Energy transformation - Wikipedia

    en.wikipedia.org/wiki/Energy_transformation

    Energy transformation, also known as energy conversion, is the process of changing energy from one form to another. [1] In physics , energy is a quantity that provides the capacity to perform work or moving (e.g. lifting an object) or provides heat .