Using resources

Question 1

what are examples of natural product that are supplemented or replaced by agricultural and synthetic products?

Answer 1

• artificial fertilisers allow us to grow more food with the land available
• chemistry helps us to provide water that is safe to drink
  -processes such as phytomining and bioleaching help us to extract metals more efficiently

Question 2

what is potable water?

Answer 2

water that is safe to drink. its not pure water because it contains dissolved substances

Question 3

explain how potable water is produced from fresh water in the UK?

Answer 3

• fresh water from rivers is passed through filter beds which removes undissolved solids
• the water is sterilised using chlorine which destroys harmful microbes

Question 4

is the UK how is most freshwater provided?

Answer 4

by rain water with low levels of dissolved substances that collects in the ground and in rivers and lakes

Question 5

how is potable water obtained in places where supplies of fresh water are limited?

Answer 5

potable water is produced by desalination of salty water or sea water. sea water has high levels of dissolved minerals.

Question 6

what 2 ways can desalination be done?

Answer 6

by distillation or reverse osmosis

Question 7

what does desalination do and what is the problem with it?

Answer 7

reduces the levels of dissolved minerals down to an acceptable level for potable water. however it requires large amounts of energy which makes them very expensive

Question 8

How is sewage waste water treated?

Answer 8

• the sewage is screened by passing it through a mesh which removes solids and pieces of grit
• the sewage is then allowed to settle in large sedimentation tanks. This produces a liquid effluent and semi solid sludge which sinks
• the sludge is taken away and digested by anaerobic bacteria. In the absence of oxygen these bacteria produce biogas which can be burned to generate electricity. The digested sludge can be used as fertiliser for farming
• the liquid effluent contains large amounts of organic molecules and harmful microorganisms which needs to be reduced before the water is returned to the environment. So air is bubbles through the liquid effluent which allows aerobic bacteria to multiply. In the presence of oxygen the aerobic bacteria digest the organic molecules and harmful microorganisms.

Question 9

What is the easiest way to produce potable water?

Answer 9

To use ground water from aquifers which is safe to drink once it’s been treated with chlorine. However they could be polluted with fertilisers from farms so need to be tested

Question 10

Describe how copper is extracted from low grade ores in phytomining

Answer 10

• grow plants on land containing copper ores
• burn the plants to produce ash
• dissolve the ash in acid to produce a solution of a copper compound
• electrolysis of the solution containing a copper compound or displace copper using scrap iron which is cheaper

Question 11

why is phytomining not widely used to extract copper

Answer 11

as high grade ores are still available and it takes a long time

Question 12

what is bioleaching?

Answer 12

• when bacteria are mixed with the low grade ore
• the bacteria carry out chemical reactions and they produce a solution called a leachate
• ## the leachate contains the metal compound we want

Question 13

what do life cycle assessments do?

Answer 13

they are carried out to asses and put a number on the environmental impact of a product in 4 stages

Question 14

what are the 4 stages of a lifecycle assesment?

Answer 14

• extracting and processing raw materials
• manufacturing and packaging
• use and operation during its lifetime
• disposal at the end of its useful life, including transport and distribution at each stage

Question 15

what are the problems with lifecycle assessments?

Answer 15

we may have to make judgments or estimates so they may not always be accurate

Question 16

how are raw materials obtained from the earth and what are the environmental impacts?

Answer 16

by quarrying which produces large amounts of dust and destroys habits
and mining which can release harmful chemicals into the environment

Question 17

how can glass bottles be reused?

Answer 17

can be crushed and melted to make different glass products

Question 18

how can metals be recycled but what is the problem?

Answer 18

by melting and then recasting or reforming into different products but different metals usually need to be separated before being recycled

Question 19

define corrosion

Answer 19

the destruction of materials by chemical reactions with substances in the environment

Question 20

how can corrosion be prevented?

Answer 20

by applying a coating that acts as a barrier such as greasing, painting or electroplating

Question 21

why doesn’t aluminium corrode?

Answer 21

as aluminium has an oxide coating that protects the metal (underneath) from further corrosion (the surface of aluminium naturally reacts with oxygen in the air)

Question 22

what is sacrificial protection?

Answer 22

• iron nails can be coated in a layer of zinc which is called galvanising. the layer of zinc acts as a barrier against air and water which prevents the iron from corroding. the zinc is more reactive than iron so prevents corrosion

Question 23

what is bronze an alloy of and what is it used for?

Answer 23

bronze is an alloy of copper and tin and is extremely hard and doesn’t corrode so is used for statues

Question 24

what is brass an alloy of and what is it used for?

Answer 24

brass is an alloy of copper and zinc and can be formed into different shapes. it can be used for musical instruments and door handles

Question 25

what is gold an alloy of and what is it used for?

Answer 25

gold is an alloy with silver, copper, and zinc to make it harder so it can be used for jewellery

Question 26

what is steel an alloy of and what is it used for?

Answer 26

steel is an alloy of carbon containing specific amounts of carbon and other metals. high carbon steel is strong but brittle and is used to make cutting tools such as chisels. low carbon steel is softer and more easily and is used to make car bodies. steel is an alloy of iron so can rust so to prevent this steel containing chromium and nickel (stainless steel) are hard and resistant to corrosion. aluminium alloys are low density.

Question 27

how is soda lime glass made and why is its use limited?

Answer 27

by heating a mixture of sand, sodium carbonate, and limestone. we then heat this mix in a furnace until it melts. when it cools it solidifies into any shape we want. its use is limited because it has a relatively low melting point.

Question 28

what is borosilicate glass and why is it more useful?

Answer 28

it has a higher melting point and is useful for objects that require heating such as kitchen wear

Question 29

how is borosilicate glass made?

Answer 29

by melting a mixture of sand and boron trioxide

Question 30

how are clay ceramics including pottery and bricks made?

Answer 30

wet clay can be shaped and then heated in a furnace

Question 31

what are composite made of?

Answer 31

- are made by combining two different materials - the reinforcement consists of fibres or fragments of one material - the reinforcement is then surrounded by a matrix or binder material

Question 32

what is a feature of composites?

Answer 32

they have different properties to the materials in them

Question 33

what do the properties of polymers depend on?

Answer 33

the monomer and the conditions used to make the polymer

Question 34

how can we change the properties of a polymer?

Answer 34

we can change the reaction temperature, the reaction pressure, or the catalyst

Question 35

what do thermosoftening polymers do when we melt them and why

Answer 35

- they melt when we heat them - so we can reshape them while they are soft - then they go back to a solid when we cool them back down - because when heated the intermolecular forces break which allows the polymer strands to separate from each other so the polymer melts. when we cool the melted polymer we reform the intermolecular forves so the polymer goes back to a solid

Question 36

what do thermosetting polymers do when we melt them and why

Answer 36

- don't melt when heated because the polymer chains are connected to eachother by strong crosslinks - the strong crosslinks are not broken by heat which is why thermosetting polymers do not melt when heated

Question 37

what elements do NPK fertilisers contain?

Answer 37

compounds of nitrogen, phosphorus, and potassium which improve agricultural productivity

Question 38

where are NPK fertilisers produced?

Answer 38

in large industrial factories where a variety of different raw materials are processed together to produce the exact fertiliser required

Question 39

what are NPK fertilisers?

Answer 39

formulations of different salts which contain the required elements in the percentages needed by the plants

Question 40

how are compounds containing nitrogen produced?

Answer 40

- main compound of nitrogen is ammonium nitrate - we use ammonia (produced by the haber process) to produce nitric acid - we then react the nitric acid with more ammonia to make ammonium nitrate

Question 41

where does the potassium come from?

Answer 41

- the potassium comes from the salts potassium chloride or potassium sulfate - both of these compounds are mined from the ground and can be used directly without any further processing

Question 42

where does the phosphate come from?

Answer 42

- phosphate rock is mined from the ground and has to be chemically processed before being used in fertilisers

Question 43

how is phosphate rock treated with nitric acid?

Answer 43

- treating phosphate rock with nitric acid produces phosphoric acid and calcium nitrate - phosphoric acid contains phosphorus but we cannot add this directly to plants, so we neutralise it with ammonia - this produces ammonium phosphate which can be used in NPK fertiliser

Question 44

how is phosphate rock treated with sulfuric acid?

Answer 44

- treating phosphate rock with sulfuric acid makes a mixture of calcium phosphate and calcium sulfate - this mixture is called single superphosphate which we can use in NPK fertilisers

Question 45

how is phosphate rock treated with phosphoric acid?

Answer 45

- treating phosphate rock with phosphoric acid makes triple superphosphate which can be used in NPK fertilisers