Chemistry Unit 1: Topic 3

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Chemistry Unit 1: Extraction of metals

What are ores?

Ores are rocks with enough metal to be considered economical to be extracted from the ground.

They are extracted through mining.

How are is the metal extracted?

In order to extract the metal from ores, a chemical reaction is needed. Only very unreactive metals such as gold can be found in their native state.

If a metal is below carbon in the reactivity series, the metal is extracted through reduction. This is done using carbon in a blast furnance, e.g. Iron Oxide.

If a metal is above carbon in the reactivity series, the metal is extracted through electrolysis. This requires lots of energy so is expensive.

Copper is extracted via smelting, which is the heating of ores in a blast furnace. The copper can then be purified through electrolysis as the purer the copper, the better it is in wiring and pipes.

Problems with extracting metals:

Ores rich in metal are now limited

Current methods of mining can be very destructive to the countryside and can cause problems for those living nearby.

New methods of extracting metals:

Phytomining- plants take in metal compounds from soil. Plants are then burnt as their ash contains these metal compounds.

Bioleaching- Bacteria absorb the metal compund and produce solutions of leachate which have metal compounds.

Scrap metals- Copper can be displaced from scrap metals such as iron because it is more reactive. E.g. iron + copper sulfate → iron sulfate + copper

Electrolysing copper salts- A current can be passed through copper salts and the positive copper ions move to the negative electrode.

What is an alloy?

An alloy is a mixture of metals, for instance iron is often mixed with carbon to produce steel.

This is because iron alone is very brittle so can snap easily.

Copper, gold, silver and aluminium are also often made into alloys as they are too weak alone.

Types of steel alloys:

Low carbon steel- easily shaped because structure is less rigid. Used in car bodies.

High carbon steel- hard because more carbon atoms prevent iron from sliding. Used in cutting tools.

Stainless steel- resists corrosion. Used in cutlery.

Transition metals

Elements in the middle section of periodic table are the transition metals. They can conduct heat and electricity and are shaped easily, all of which makes them useful in structures.

Copper is useful in plumbing and wiring because it does not reatc with water, can be shaped yet is hard enough for plumbing and is a good conducter.

Aluminium and titanium are also useful because of their low densities and do not corrode easily.

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