Literally a change in form. Metamorphism is a word that can be applied to rocks or insects. A maggot metamorhoses into a fly, a caterpillar metamorphoses into a butterfly and limestone metamorphoses into marble. When applied to rocks, heat, pressure or both are involved. Collisions between the plates of the Earth create these high pressure and high temperature conditions. Rocks formed in this way are called metamorphic rocks.

When a substance burns, oxygen from the air is needed. That is because burning is an oxidation reaction. The oxygen reacts chemically with each of the atoms in the substance that is burning to form oxides. For example, magnesium burns to form magnesium oxide, so we say the magnesium has been oxidised. Where there are more than one atoms in the material that is being burnt, each different atom needs to be considered. Sugar consists of atoms of carbon, hydrogen and oxygen joined to each other. The oxidation products from burning sugar will be:

This is a list of all the elements represented by their symbols. The order in which they appear depends partly on how heavy their atoms are (hydrogen has the lightest) but also upon the structure of the atoms. The vertical columns are families of similar elements called groups. Each group has a number. This number tells you the number of electrons in the outer electron shell of the elements in the group. The horizontal rows are called periods. Each element in a period has one electron more (or less) than its neighbour.

The chemical removal of oxygen from a compound for example the reaction between carbon monoxide and iron oxide in the Blast Furnace.

The iron oxide has had oxygen removed and is therefore said to have been reduced. Note how the carbon monoxide has become the dioxide - oxygen has been added so that compound has been oxidised. When oxidation and reduction take place together, we call the reaction a redox reaction.

At higher levels at GCSE, reduction is a gain of electrons - the opposite of oxidation. The phrase "OiL RiG" helps you to remember this - OiL = Oxidation is Loss (or electrons), you work out what RiG stands for!

The bending of light. A light ray that hits a transparent surface at an angle other than 90 degrees will bend as it crosses the surface. If the light is travelling into a more dense medium (e.g. from air into water), the light will bend towards the normal and vice-versa. It does this because it travels more slowly in the more dense medium.

Salts are compounds that are formed whenever acids react. For example, when hydrochloric acid dissolves zinc, a salt called zinc chloride is formed.

A metamorphic rock that has been formed under high pressure. It was originally a sedimentary rock called shale or possibly a mudstone, which is like a less brittle type of shale. The particles that make up slate have become aligned in the same direction by the pressure, so shale splits easily into flat sheets.

This is a word used to describe something that will dissolve. Usually it means something that will dissolve in water but not always. If it doesn't mean in water, the solvent will be quoted e.g. tar is soluble in petrol. Common mistakes are to spell it with an 'a' after the 'u' or to say that something is 'a soluble'.

A substance that will dissolve something else. Water is a solvent for many things and I have heard it referred to as the universal solvent. In non-scientific terms, a solvent is taken to mean a harmful material that has been used in the manufacture of something like glue or paint and is and is sniffed as a drug.

Each element has its own symbol which is made of a letter or letters from its name or from some other word. For example, carbon has the symbol C but iron has the symbol Fe from its Latin name.

This describes how runny something is. A non-viscous liquid is very runny (e.g. water, petrol) whereas a viscous liquid (e.g. syrup, tar) are not very runny.

This describes how easily something will evaporate. Something like ethanol has a high volatility whereas something like tar has a low volatility.