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| Letter | Equation | Variables |
|---|---|---|
| M | Einstein's Relativity | M=E/c2, where M=Mass, E=Energy, c=Speed of Light |
| i | Imaginary Number | i = √-1 |
| n | Ideal Gas Law | n = PV/RT, where n=number of moles, P=Pressure, V=Volume, T=Temperature, R=Universal Gas Constant |
| e | Exponetial Function | e = ∑1/n!, where n!=n factorial |
| s | System Entropy | s=H-G/T, where S=Entropy, H=Enthalpy, G=Gibbs free energy, T=Temperature |
Entropy (S) is a measure of the disorder or randomness of a system. An ordered system has low entropy. A disordered system has high entropy. For example, in the solid state, molecules are strongly attracted to each other (less disorder). In the gaseous state, molecules are not strongly attracted (more disorder). Because of that, entropy is greater in a gas.
Enthalpy (H) is the sum of internal energy U of a system and the product of the pressure and change in volume of the system at a constant pressure.
In thermodynamics, the Gibbs free energy (also known as free enthalpy to distinguish it from Helmholtz free energy) is a thermodynamic potential that can be used to calculate the maximum or reversible work that may be performed by a thermodynamic system at a constant temperature and pressure (isothermal, isobaric).
The mole is the unit of measurement in the International System of Units (SI) for amount of substance. It is defined as the amount of a chemical substance that contains as many representative particles, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of carbon-12 (12C), the isotope of carbon with relative atomic mass 12 by definition. This number is expressed by the Avogadro constant, which has a value of 6.022140857(74)×1023 mol−1, which is just over 602 sextillion. The mole is one of the base units of the SI, and has the unit symbol mol.
The Universal Gas Constant is a constant (also known as the molar, universal, or ideal gas constant, denoted by the symbol R) that is a physical constant which is featured in many fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation. The gas constant value is 8.3144598 J⋅mol−1⋅K-1