Chemistry definitions

Mixture

Contains two or more substances not chemically joined together.

Alloy

A mixture that contains at least one metal.

Compound

A substance formed when two or more different elements are chemically joined together.

Formula

The number of atoms of each element in a compound.

Chemical Equation

An equation to show reagents changing into products.

Reagent

Chemicals at the start of a chemical reaction.

Product

Chemicals that are formed during a chemical reaction.

Combustion

A reaction in which a fuel combines with oxygen and gives out energy and a flame.

Exothermic

A reaction that gives out energy (gets hotter).

Endothermic

A reaction that takes in energy (gets colder).

Precipitation

A reaction in which a solid is produced from at least one solution.

Decomposition

A reaction in which a compound is broken down into simpler substances.

Thermal Decomposition

A reaction in which a compound is broken down by heat into simpler substances.

Synthesis

A reaction in which two or more substances combine to form a more complex product.

Displacement

A reaction in which a more reactive element takes the place of a less reactive element in a compound.

Effervescence

A fizzing made when a gas is produced.

Precipitate

Cloudy, insoluble solid product formed during a precipitation reaction.

Oxide

An element combined with oxygen to form a new compound.

Base

A substance with a pH of 8-14.

Alkali

A soluble base, also has a pH of 8-14.

Acid

A substance with a pH of 0-6.

Indicator

A substance that changes color when in different pH.

pH

A scale to measure the acidity or basicity of a chemical.

Neutralisation

When an acid reacts with a base to form salt and water only.

Salt

A compound formed when the hydrogen of an acid is replaced by a metal.