Edexcel GCSE Chemistry key terms

A measure of how acidic or alkaline a solution is; a lower pH corresponds to a higher hydrogen ion concentration.

The process in which photosynthetic organisms use light energy to make glucose from carbon dioxide and water, releasing oxygen.

A numerical scale used to describe how acidic or alkaline a solution is.

A change between physical states in which no new substance is produced.

A characteristic of a material that can be observed or measured, such as density, strength or electrical conductivity.

The form of a substance—solid, liquid or gas—under the stated conditions.

A biological extraction method in which plants absorb metal ions from soil through their roots and concentrate them in their tissues.

A flat section of a temperature–time graph where the temperature stays constant.

Thomson’s model of an atom as a ball of positive charge with negative electrons embedded in it.

A substance introduced into the environment that can cause harm to living organisms or the surroundings.

An ion formed from two or more chemically joined atoms that act as a single charged unit, such as $\mathrm{OH^-}$ or $\mathrm{SO_4^{2-}}$.

A polymer containing many ester links in its chain.

A simple polymer whose large molecules contain long chains of carbon atoms bonded to hydrogen atoms.

A very large molecule made by joining many smaller molecules together.

The continuous chain of bonded atoms running through a polymer molecule; in the addition polymers considered here, it is a carbon chain.

The reaction in which many monomer molecules join together to form a polymer.

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

A test result showing that the ion being tested for is present.

Water that is safe to drink; it need not contain only water molecules.

A substance being tested to find out whether, and how effectively, it catalyses a particular reaction.

The loss of desired product while it is transferred, separated, purified or collected.

An action taken to reduce the chance or severity of harm while working.

An insoluble solid formed in a solution during a precipitation reaction.

A reaction in which dissolved substances form an insoluble solid.

A conclusion about an unknown case based on an established pattern and relevant evidence.

Early, relatively simple photosynthetic organisms that used carbon dioxide and released oxygen.

A substance formed by a chemical reaction.