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  2. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    For a similar process at constant temperature and volume, the change in Helmholtz free energy must be negative, <. Thus, a negative value of the change in free energy (G or A) is a necessary condition for a process to be spontaneous. This is the most useful form of the second law of thermodynamics in chemistry, where free-energy changes can be ...

  3. Negative energy - Wikipedia

    en.wikipedia.org/wiki/Negative_energy

    The negative-energy particle then crosses the event horizon into the black hole, with the law of conservation of energy requiring that an equal amount of positive energy should escape. In the Penrose process , a body divides in two, with one half gaining negative energy and falling in, while the other half gains an equal amount of positive ...

  4. Redox gradient - Wikipedia

    en.wikipedia.org/wiki/Redox_gradient

    Start points of arrows indicate energy associated with half-cell reaction. Lengths of arrows indicate an estimate of Gibb's free energy (ΔG) for the reaction where a higher ΔG is more energetically favorable (Adapted from Libes, 2011). [3] A redox gradient is a series of reduction-oxidation reactions sorted according to redox potential.

  5. Heat equation - Wikipedia

    en.wikipedia.org/wiki/Heat_equation

    For heat flow, the heat equation follows from the physical laws of conduction of heat and conservation of energy (Cannon 1984). By Fourier's law for an isotropic medium, the rate of flow of heat energy per unit area through a surface is proportional to the negative temperature gradient across it: =

  6. Geothermal gradient - Wikipedia

    en.wikipedia.org/wiki/Geothermal_gradient

    Negative geothermal gradients may also occur due to deep aquifers, where heat transfer from deep water by convection and advection results in water at shallower levels heating adjacent rocks to a higher temperature than rocks at a somewhat deeper level. [34] Negative geothermal gradients are also found at large scales in subduction zones. [35]

  7. Chemiosmosis - Wikipedia

    en.wikipedia.org/wiki/Chemiosmosis

    Directions of chemiosmotic proton transfer in the mitochondrion, chloroplast and in gram-negative bacterial cells (cellular respiration and photosynthesis). The bacterial cell wall is omitted, gram-positive bacterial cells do not have outer membrane. [6] The complete breakdown of glucose releasing its energy is called cellular respiration. The ...

  8. Heat transfer - Wikipedia

    en.wikipedia.org/wiki/Heat_transfer

    Radiative heat transfer is the transfer of energy via thermal radiation, i.e., electromagnetic waves. [1] It occurs across vacuum or any transparent medium ( solid or fluid or gas ). [ 15 ] Thermal radiation is emitted by all objects at temperatures above absolute zero , due to random movements of atoms and molecules in matter.

  9. Electrochemical gradient - Wikipedia

    en.wikipedia.org/wiki/Electrochemical_gradient

    An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts: The chemical gradient, or difference in solute concentration across a membrane. The electrical gradient, or difference in charge across a membrane.