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Chemistry > Using resources > Flashcards

Using resources Flashcards

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1
Q

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

A
  • 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
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2
Q

what is potable water?

A

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

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3
Q

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

A
  • fresh water from rivers is passed through filter beds which removes undissolved solids
  • the water is sterilised using chlorine which destroys harmful microbes
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4
Q

is the UK how is most freshwater provided?

A

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

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5
Q

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

A

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

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6
Q

what 2 ways can desalination be done?

A

by distillation or reverse osmosis

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7
Q

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

A

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

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8
Q

How is sewage waste water treated?

A
  • 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.
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9
Q

What is the easiest way to produce potable water?

A

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

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10
Q

Describe how copper is extracted from low grade ores in phytomining

A
  • 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
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11
Q

why is phytomining not widely used to extract copper

A

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

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12
Q

what is bioleaching?

A
  • 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
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13
Q

what do life cycle assessments do?

A

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

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14
Q

what are the 4 stages of a lifecycle assesment?

A
  • 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
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15
Q

what are the problems with lifecycle assessments?

A

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

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16
Q

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

A

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

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17
Q

how can glass bottles be reused?

A

can be crushed and melted to make different glass products

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18
Q

how can metals be recycled but what is the problem?

A

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

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19
Q

define corrosion

A

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

20
Q

how can corrosion be prevented?

A

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

21
Q

why doesn’t aluminium corrode?

A

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)

22
Q

what is sacrificial protection?

A
  • 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
23
Q

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

A

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

24
Q

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

A

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

25
Q

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

A

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

26
Q

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

A

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.

27
Q

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

A

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.

28
Q

what is borosilicate glass and why is it more useful?

A

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

29
Q

how is borosilicate glass made?

A

by melting a mixture of sand and boron trioxide

30
Q

how are clay ceramics including pottery and bricks made?

A

wet clay can be shaped and then heated in a furnace

31
Q

what are composite made of?

A
  • 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
32
Q

what is a feature of composites?

A

they have different properties to the materials in them

33
Q

what do the properties of polymers depend on?

A

the monomer and the conditions used to make the polymer

34
Q

how can we change the properties of a polymer?

A

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

35
Q

what do thermosoftening polymers do when we melt them and why

A
  • 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
36
Q

what do thermosetting polymers do when we melt them and why

A
  • 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
37
Q

what elements do NPK fertilisers contain?

A

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

38
Q

where are NPK fertilisers produced?

A

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

39
Q

what are NPK fertilisers?

A

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

40
Q

how are compounds containing nitrogen produced?

A
  • 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
41
Q

where does the potassium come from?

A
  • 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
42
Q

where does the phosphate come from?

A
  • phosphate rock is mined from the ground and has to be chemically processed before being used in fertilisers
43
Q

how is phosphate rock treated with nitric acid?

A
  • 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
44
Q

how is phosphate rock treated with sulfuric acid?

A
  • 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
45
Q

how is phosphate rock treated with phosphoric acid?

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

Chemistry (7 decks)

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