Chemistry terms: G

G

Galvanizingalso galvanized, galvanised, galvanising

Coating iron or steel with a layer of zinc. The zinc is oxidized in preference to the iron, so it protects the iron even where the coating is scratched.

Introduced in R3.2 Electron transfer reactions

Gas constantalso molar gas constant, R

The constant $R$ in the ideal gas equation, $8.31\ \text{J K}^{-1}\ \text{mol}^{-1}$.

Introduced in S1.5 Ideal gases

general formulaalso general formulas

A formula in terms of n that fits every member of a homologous series, such as ${{\mathrm{C}{\vphantom{X}}_{\smash[t]{n }}\mathrm{H}{\vphantom{X}}_{\smash[t]{2n +2}}}}$

Gibbs energyHL only · also Gibbs free energy, free energy, G

A property of a system, $G = H - TS$, that combines its enthalpy and entropy; at constant temperature and pressure a system changes spontaneously towards lower Gibbs energy.

Introduced in R1.4 Entropy and spontaneity

Gibbs energy changeHL only · also Gibbs free energy change, free energy change, ΔG, standard Gibbs energy change

The quantity $\Delta G = \Delta H - T\Delta S$ for a change at constant temperature and pressure, in $\text{kJ mol}^{-1}$. A negative value means the change is spontaneous; at equilibrium $\Delta G = 0$

Global warming potentialalso GWP

The warming caused by a given mass of a gas over a stated period, usually 100 years, relative to the same mass of carbon dioxide (GWP = 1).

Introduced in R1.3 Energy from fuels

graphene

A single layer of graphite, one atom thick: a very strong, light, flexible sheet that conducts electricity and heat well.

Introduced in S2.2 The covalent model

graphite

An allotrope of carbon made of layers of hexagonal rings, each atom bonded to three others with one delocalized electron; the layers are held by London forces, so it is soft and conducts electricity.

Introduced in S2.2 The covalent model

Gravimetric analysisalso gravimetric

A method of analysis in which the amount of a substance is found by weighing, for example by precipitating it as an insoluble solid that is filtered, dried and weighed.

Introduced in R2.1 How much? The amount of chemical change

Green chemistryalso sustainable chemistry

The design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances, for example by high atom economy, safer solvents, catalysts, lower energy use and renewable feedstocks.

Introduced in R2.1 How much? The amount of chemical change

Greenhouse effect

The warming of the Earth's surface and lower atmosphere caused by gases that absorb infrared radiation emitted by the surface and re-emit some of it back towards the surface.

Introduced in R1.3 Energy from fuels

Greenhouse gasalso greenhouse gases

A gas in the atmosphere that absorbs infrared radiation, such as carbon dioxide, methane, water vapour, dinitrogen monoxide, ozone and CFCs.

Introduced in R1.3 Energy from fuels

ground statealso ground states

The lowest-energy arrangement of the electrons in an atom or ion.

Introduced in S1.3 Electron configurations

Groupalso groups

A vertical column of the periodic table, numbered 1–18. Elements in the same group have the same number of valence electrons and similar chemical properties.

Introduced in S3.1 The periodic table: classification of elements