GCSE Chemistry C10 - Using Resources

natural resources

- supplemented by agriculture

- provide food, timber, clothing, fuels

finite resources

- from the earth, oceans and atomosphere which are processed to provide energy and materials

- limited supply that will eventually run out

why is chemistry good for improving agriculture

- provide new products and in sustainable environment

- meets the needs of current generations without comprimising the ability of future generations to meet their own needs

renewable energy resources

- sources of power that quickly replenish themselvbes and can be used again (plants/wood if they continue to be re-planted)

alternative methods of extracting metals

because ores are limited, copper ores are scarce so there are new wqays of extracting copper from low-grade ores. phytomining and bioleaching. these methods avoid traditional mining methods and moving and disposing of large amounts of rock

phytomining and bioleaching

phytomining: uses plants to absorb metal compounds (copper ions) are grown on soil containing low grade copper ore. the plants are burned to produce ash that contains metal compounds. The metal compounds can be leached (dissolved) from the ash by adding sulphuric acid. This makes a solution of copper sulphate. Displacement by the scrap iron and then electrolysis make pure copper metal

bioleaching: uses bacteria to produce leachate solutions. they feed on low grade metal ores, by a combination of biological and chemical processes

advantages of bioleaching and phytomining

bioleaching: no need for high temps, 20% of copper comes from bioleaching and is likely to increase

phytomining: sustainable, cost effective, improve biodiversity, reduces rock waste

disadvantages of bioleaching and phytomining

bioleaching: slow process as it takes years to extract 50% of metal from low grade metal, produces toxic substances such as sulphuric acid which is harmful to the environment

phytomining: wait for plants to grow, requires specific plant species, requires lots of energy

corrosion

destruction of materials by chemical reactions with substances in the environment

e.g. rusting. iron needs both air and water to rust

how can corrosion be prevented

barriers: lubricates the moving parts so they reduce friction so it rusts slower. paint, grease act as a barrier. can be washed away or scratched

aluminium has an oxide coating that protects the metal from further corrosion

galvanising: some coatings are reactive and contain a more reactive metal to provide sacrificial protection such as zinc is used to galvanise iron. zinc oxide layer can be removed and replaced. it donates electrons to any irons of the other metal that may have formed so they don't corrode

alloys as useful materials

some metals are too soft so they are mixed with small amounts of similar metals to make them harder for everyday use.

electroplating

coating a metal with a thin layer of another metal by electrolysis to improve the metal's corrosion resistance

bronze and brass as an alloy

bronze - alloy with copper and tin which is used in electrical connectors

brass - alloy with copper and zinc for tools

steel as an alloy

- mixed with carbon and iron

- low-carbon steels are easioly shaped which ca be used for sheeting (malleable)

- stainless steels (containing chromium and nickel) are resistant to corrosion which is used for cutlery

- hard carbon steel is strong but brittle and is used for cutting tools

alluminium as an alloy

- low density and so used for aircraft