Year 9 Chemical Reactions Key Words

Chemical reactions (Year 9)

Greenhouse Effect

The retention of heat in the atmosphere caused by the build-up of greenhouse gases.

Atmosphere

The layers of gases that surround the Earth. The important gases in the atmosphere are nitrogen, oxygen and carbon dioxide.

Atoms

The smallest part of an element that can exist.

Balancing Equations

A chemical equation written using the symbols and formulae of the reactants and products, so that the number of units of each element present is the same on both sides of the arrow.

Combustion

The process of burning by heat.

Complete Combustion

Burning in a plentiful supply of oxygen or air. Complete combustion of a hydrocarbon produces water vapour and carbon dioxide.

Compounds

A substance formed by the chemical un ion of two or more elements.

Conservation of Mass

Mass is never lost or gained throughout a reaction& atoms are just changed from one form into another.

Elements

A substance made of one type of atom only.

Fuel

Any compound that has stored energy.

Impact

The effect or influence of an act.

Incomplete Combustion

Burning when there is a limited supply of air or oxygen.

Ozone Layer

A layer of the earth`s atmosphere, that absorbs most of the ultraviolet (UV) radiation from reaching the earth.

Atomic Mass

The number of protons in the nucleus of an atom. Also called the proton number.

Relative Formula Mass

The relative formula mass (M_r) of a compound is calculated by adding together the relative atomic masses (A_r) of the atoms present in a compound.

Relative Atomic Mass

The mean relative mass of the atoms of the different isotopes in an element. It is the number of times heavier an atom is than one-twelfth of a carbon-12 atom.