Rocks and Metals - Rocks and the Earth

Plate Tectonics

The crust is not all one piece but is made up of sections called plates. These plates are floating about on the mantle and moving.

At places where the plates are colliding earthquakes and volcanoes occur . Where plates are colliding the more dense plate is forced underneath the less dense plate. These places are called subduction zones.

Reactivity of Metals

Some metals are happy as pure elements. Some others are desperate to react .

Order of reactivity

A more reactive metal can displace a weaker one from one of

. Potassium K one of its solutions.

2. Sodium Na

3. Calcium Ca eg If zinc is put into copper sulphate solution then copper metal

4. Magnesium Mg and zinc sulphate solution is formed.

5. Aluminium Al

6. Zinc Zn Zinc + Copper Sulphate Zinc Sulphate + Copper

7. Iron Fe

8. Lead Pb Zn + Cu SO4 ZnSO4 + Cu

9. Copper Cu

0. Silver Ag

1. Gold Au

Making Metals from Ores

Only the most unreactive metals like silver and gold are found in nature as pure metals.

Most metals must be made from rocks which contain compounds of the metal. These special rocks are called ores.

Many useful substances can be made from ores such as pottery , cement ,glass and most metals.

Less reactive metals such as copper and iron can be made from the minerals in their ores by heating their ores with carbon or carbon monoxide gas.

Eg Iron can be made from the mineral Haemetite by heating this with carbon monoxide gas.

Iron oxide + Carbon Monoxide Iron + Carbon Dioxide

FeO + CO Fe + CO2

Electolysis

Reactive metals require a more powerful method to purify them from their ores .

This more powerful method involves splitting the compound in the ore by passing electricity through the compound. This method is called electrolysis.

For electrolysis to work the ions (charged particles ) that the compound is made up of must be free to move . This can be achieved either by melting or dissolving the compound.

The electrode that is positively charged is called the anode.

The electrode that is negatively charged is called the cathode.

Making Copper

A boulder containing copper ores is connected to the anode and put into copper sulphate solution. Pure copper is used as the cathode. As electrolysis is carried out the cathode is coated in pure copper and the boulder containing copper ores dissolves . Rock impurities fall to the bottom of the chamber.

Making Aluminium

Aluminium is made by doing electrolysis on bauxite which is an ore which contains the compound aluminium oxide.

Aluminium oxide is insoluble so to enable electrolysis to be done it must be melted.

Aluminium oxide does not melt until 2045oC so cryolite is added to it to make it melt at about 1000oC

Graphite anodes are used in the electrolysis and at the anode oxygen gas is formed.

The casing is the cathode and liquid aluminium metal is formed there.

Atoms , Molecules and Ions

All matter is made up of tiny particles called atoms. These particles have no charge.

A substance only made of one type of atom is called an element.

When a chemical reaction occurs atoms bond together to make new particles called molecules.

A compound is always made up of molecules. Some elements are made up of molecules.

C

Oxygen Oxygen Carbon dioxide

Atom molecule molecule

Structure of Atoms

An atom is made up of two parts. In the centre there is a small , heavy lump with a positive charge called the nucleus. On the outside small light ,negatively charged particles called electron orbit around the nucleus.

Nucleus (+ve)

Electrons (-ve)

An Atom

Oxidation and Reduction

When a substance reacts with oxygen this is called oxidation.

When a substance has oxygen remove this is called reduction