The hardest part of any revision process is getting started. These brief notes do not tell you the whole story but they might help you to get started and, pretty soon you will be amazed at how much you actually know.

There are three main sections you need to know about for the examination.

Rocks and building (including quite a bit on atomic structure)

All substances are made of atoms.

The atoms themselves contain a nucleus (containing protons and neutrons) surrounded by electrons.

An atom is the smallest particle that can be recognised as being an element.

The periodic table shows a list of elements.

The elements are substances that only contain one kind of atom.

Atoms of elements have a chemical symbol. The first letter is always a capital letter. The second letter (if it has one) is always a lower case. Be careful that your handwritten lower case “l” does not look like a capital “L”.

The periodic table collects elements with similar properties in vertical columns called groups.

Atoms join together (bond) by gaining, losing or sharing electrons to form compounds.

The chemical formula of a substance shows the number of each kind of atom that are joined together. For an ionic compound, the formula shows the ratio of each kind of atom.

In any chemical reaction, the total mass of the starting materials (reactants or reagents) is always the same as the total mass of the materials at the end (products). Sometimes you might be confused in this because some substance may be added or taken away that are not included in your weighings.

Chemical equations (symbol ones) must always be balanced. That is they must have the same number of each kind of atom on both sides.

Limestone is a building material. It has the chemical name calcium carbonate.

Limestone can also be used to make quicklime (calcium oxide), slaked lime (calcium hydroxide), cement and glass.

Most metal carbonates decompose on heating (thermal decomposition) to give the metal oxide and carbon dioxide gas. This is done to limestone in a lime kiln to form quicklime.

Sodium carbonate and potassium carbonate are two carbonates that cannot be decomposed using a Bunsen burner flame.

Rocks and metals

Metals are obtained from ores which are dug out of the Earth.

Apart from for the very unreactive metals, chemical reactions are needed to extract the metal. Many of these reactions require a great deal of energy, either to run the reaction itself or to provide the raw materials.

A metal that is mixed (ie not a compound) with other elements is called an alloy.

Alloys usually have different properties from their parent metals and alloys with specific properties can be designed. In particular, aluminium, titanium, iron, copper and gold are useful and so are their alloys.

Recycling metals is a good way to conserve the Earth’s resources of these metals.

Recycling also saves energy resources because it is much less energy-demanding to re-use a metal than have to extract fresh metal from its ore.

Crude oil

Hydrocarbons are molecules that contain only hydrogen and carbon atoms.

Crude oil is almost entirely made up of a mixture of hydrocarbons.

Most of the hydrocarbons in crude oil are saturated hydrocarbons (hydrocarbons with only single bonds).

The family of saturated hydrocarbons is called the alkanes.

All alkanes have the same general chemical formula (C_nH_2n+2).

Crude oil is broken down into groups of molecules with similar boiling points by fractional distillation.

Many of the fractions of crude oil are used as fuels.

Burning fuels causes pollution of the atmosphere.

Carbon dioxide (a product of burning) is a “greenhouse gas” and contributes to global warming.

Sulfur dioxide is formed because there are sulphur impurities in crude oil that are not removed at the fractional distillation stage. When the sulphur burns, it forms sulphur dioxide which as well as being an irritant also contributes to acid rain.

Particulate matter is also released from burning fossil fuels.

Chemists are trying to produce less polluting fuels (such as ULS petrol).

Pollution would also be reduced if less fuel were used.