GeologyRocks

Enthalpy

A measure of internal energy of a system. For a gas:

H=E+pV

Where H is the enthalpy, E is the internal energy, p is the pressure and V is the volume.

Entropy

In thermodynamics entropy is the amount of energy not available to do work.

Gibbs Free Energy

Chemical reactions can be made to do work (e.g. produce heat). Energy which is, or which can be, available to do useful work is called Gibbs free energy (G).

G = H - TS

Where H is the enthalpy, S is the entropy, and T is the absolute temperature.

Oxidation

A chemical reaction in which substances combine with oxygen for form an oxide. For example, the combination of iron with oxygen to form an iron oxide (rust) or copper and oxygen produce copper oxide; the green coating on old pennies. The opposite of oxidation is reduction.

Supersaturation

Supersaturation is the dissolving of a larger quantity of solute in a solution than would normally be possible. For example sea water is supersaturated with respect to carbonate by a factor of 3 or 4.