Chemistry key terms

The force of attraction between particles with opposite electric charges.

The force of attraction between particles with opposite electric charges.

A pure substance made from only one type of atom.

The release of radiation by matter.

An instrumental technique that identifies elements by analysing the wavelengths of light emitted by a hot sample.

A pattern of light at particular wavelengths produced by a substance; each metal ion produces a characteristic emission spectrum.

A chemical formula showing the simplest whole-number ratio of the different atoms or ions in a compound.

The sum of the relative atomic masses represented by one empirical formula unit.

The management of a product when it is no longer useful, which may include reuse, recycling, incineration or landfill.

The point at which a product is no longer useful, when it may be reused, recycled, treated or disposed of.

A reaction or change that takes in heat energy from the surroundings.

A change that takes in heat energy from the surroundings.

A reaction direction that takes in energy from the surroundings.

A process that takes in energy from the surroundings.

A reaction that takes in energy from its surroundings.

The point in a titration at which the indicator shows a lasting colour change.

An observable point chosen to stop timing a reaction, such as a specified colour change.

The energy transferred overall during a chemical reaction; it equals the energy needed to break bonds minus the energy released when new bonds form.

The proportion of the energy supplied to a device or process that is transferred usefully rather than wasted.

A region around the nucleus that electrons with similar energies occupy; also called an electron shell.

The movement of energy from one place or set of substances to another; energy is not created or destroyed.

A control that physically separates people from a hazard, such as a fume cupboard or safety screen.

An individual object being counted, such as an atom, molecule, ion or formula unit.

A factor concerning the natural world, such as resource use, waste, pollution, habitats or long-term sustainability.

A stage or process that makes a particularly large contribution to an environmental impact.

A change to the environment caused by an activity, such as using up resources, releasing pollution or producing waste.

A biological catalyst that speeds up a reaction without being used up.

A mathematical statement showing that two expressions have the same value, written with an equals sign.

The mass represented by a substance in a balanced equation, calculated as its coefficient multiplied by its $M_r$.

The relative amounts of reactants and products present in a system at equilibrium.