Extracting metals

Page 1

Extracting Metals- The reactivity series

Most reactive element is placed at the top and the least reactive element at the bottom

REACTIVITY SERIES- STARTING FROM THE MOST REACTIVE METAL

Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold

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How elements react with water?

Potassium Reacts Violently/ Sodium Reacts Very quickly/ Lithium Reacts Quickly/ Calcium Reacts More slowly

How elements react with dilute acid?

Calcium Reacts Very quickly/ Magnesium Reacts Quickly/ Zinc Reacts More slowly/ Iron Reacts More slowly than zinc/

Silver Barely Reacts/ Gold Doesn’t React

If something gains oxygen it is oxidised. Reduction is the removal of oxygen

Page 2

Extracting Metals- Displacement Reaction

A more reactive metal will displace a less reactive metal from a compound

aluminium + iron(III) oxide → iron + aluminium oxide

Because aluminium is more reactive than iron, it displaces iron from iron(III) oxide. The aluminium removes oxygen from the iron(III) oxide:

iron is reduced

aluminium is oxidised

When oxidation and reduction occur at the same time it is called Redox reaction.

Displacement reactions are examples of redox reactions

Page 3

Extracting Metals-Extracting metals using carbon

An ore is a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile:

low-grade ores contain a small percentage of the metal or its compound

high-grade ores contain a larger percentage

Unreactive metals such as gold are found in the Earth's crust as the uncombine elements. However, most metals are found combined with other elements to form compounds.

Metals higher than carbon in the reactivity series have to be extracted using electrolysis which is expensive.

Metals below carbon in the reactivity series can be extracted using Carbon

This is because carbon can only take the oxygen away from metals which are less reactive than carbon itself.

Gold and silver are found as uncombine elements

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Extracting Metals-Other methods of extracting metals

Electrolysis is more expensive than Reduction with carbon

For electrolysis you need a huge abundance of electricity, which is expensive. There are also costs in melting the metals.

Extracting metals using the reduction of carbon is much cheaper. Carbon is cheap so the process would also be cheaper

There are biological methods in extracting metals

There are less ores found in the earth

And there has become more demand for these ores

Scientists have found easier and more efficient ways to extract metals from their ores

Bioleaching- Uses bacteria to separate metals from their ores. Bacteria gets its energy from bonds between the atoms in the ore, separating out the metals from the ore during this process. The solution produced by the process (leachate) contains metal ions which can be extracted by electrolysis or displacement reaction.

Phytoextraction- Growing plants in soil that contains metal compounds. Plants can't use or get rid of metals so they gradually build up in the leaves. Plants can be harvested dried and burned in a furnace. The ash collected contains metal compounds from which metals can be extracted by electrolysis or displacement reaction

Page 5

Extracting Metals-Recycling

Recycling conserves resources and energy

Raw material extraction takes loads of energy which comes from fossil fuels

Fossil fuels are running out important to conserve them

Recycling saves energy as process uses a small fraction of energy needed to to extract and refine materials from scratch

Recycling protects the environment

Mines are damaging environments and destroys habitats. Recycling metals reduces mines

Recycling materials also cuts down landfills. Landfills increase pollution rapidly and takes a huge amount of space.

Recycling has economic benefits

Recycling saves money

Recycling expensive things to buy and extract is really beneficial

It is a massive industry and creates loads of jobs

Page 6

Extracting Metals-Life cycle assessment

It’s the stages of the products life

Stage 1. Choice of material

Metals be mined and extracted from their ores. These processes need a lot of energy and causes loads of pollution

Raw materials for chemical manufactures come from crude oil. Which is a non-renewable resource. Obtaining it requires loads of energy and pollution

Stage 2- Manufacture

Uses a lot of energy and other resources

Cause pollution

Think about any waste products and how to dispose them

Some waste gets recycled and used usefully.

Stage 3- Product use

Using product damages, the environment

Paint from product gives toxic fumes

Burning fuels releases greenhouse gases

Stage 4- Disposal

Products disposed into landfill

Takes a lot of space and pollutes land and water

Product could be burnt and cause air pollution

Page 7

Extracting metals- Questions from Spec

Q. Deduce (Explain) the relative reactivity of some metals, by their reactions with water, acids and salt solutions

A.

How elements react with water?

Potassium Reacts Violently/ Sodium Reacts Very quickly/ Lithium Reacts Quickly/ Calcium Reacts More slowly

How elements react with dilute acid?

Calcium Reacts Very quickly/ Magnesium Reacts Quickly/ Zinc Reacts More slowly/ Iron Reacts More slowly than zinc/

Silver Barely Reacts/ Gold Doesn’t React

Q. What is displacement reaction?

A. It is a redox reaction in which there is oxidation and reduction occurring at the same time.

Q. What does a cation mean?

A. A positively charged ion

Q. Where are most metals extracted from?

A. From the ore found in the Earth's crust

Q. What are unreactive metals found as/ and where are they found?

A. Found in the Earth’s crust as the uncombined elements

Page 8

Extracting metals- Questions from Spec

Q. What does oxidation mean?

A. The gain of oxygen

Q. What does reduction mean?

A. The loss of oxygen

Q. Why are metals extracted by heating carbon?

A. These happens because a metal is less reactive than carbon and it can be extracted from its oxides by heating with carbon. The carbon displaces metal from the compound and removes the oxygen from the oxide.

Q. Why are some metals extracted by electrolysis?

A. Because they cannot be heated by carbon as carbon is less reactive than these metals. And it requires a lot of energy to extract these metals.

Q. Evaluate alternative biological methods of metal extraction

A.

Bioleaching- Uses bacteria to separate metals from their ores. Bacteria gets its energy from bonds between the atoms in the ore, separating out the metals from the ore during this process. The solution produced by the process (leachate) contains metal ions which can be extracted by electrolysis or displacement reaction.

Phytoextraction- Growing plants in soil that contains metal compounds. Plants can't use or get rid of metals so they gradually build up in the leaves. Plants can be harvested dried and burned in a furnace. The ash collected contains metal compounds from which metals can be extracted by electrolysis or displacement reaction

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Page 9

Extracting metals- Questions from Spec

Q. Explain how a metal’s relative resistance to oxidation is related to its position in the reactivity series

A. A metal's relative resistance to oxidation is related to its position in the reactivity series - in general, the lower down a metal is, the greater its resistance to oxidation When a metal reacts with a dilute acid, a salt and hydrogen are formed.

Q. Evaluate the advantages of recycling metals

A. More economic - less energy is needed to produce a metal less damage to the environment - fewer quarries and mines, less noise and less heavy traffic saves valuable raw materials - reserves of metal ores will last longer

Q. What is the life cycle assessment for a product?

A. Consideration of the effect on the environment of obtaining the raw materials, manufacturing the product, using the product and disposing of the product when it is no longer useful