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Chemistry Paper 2 > Using Resources > Flashcards

Using Resources Flashcards

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1
Q

Drinking water must have:

A
  • low levels of dissolved salts

- cannot have high levels of microbes like bacteria

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2
Q

What is potable water?

A
  • water that is safe to drink

- and contains dissolved substances such as mineral ions

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3
Q

What provides most potable water in the UK?

A
  • rainwater, as it contains low levels of dissolved substances
  • it collects in the ground in aquifers and in lakes, rivers and sewers.
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4
Q

How to produce potable water?

A
  • choose a source of freshwater
  • then pass the water through filter beds: this removes materials such as leaves and suspended particles
  • sterilise the water to kill microbes using chlorine
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5
Q

How do you produce potable water from seawater?

A
  • desalination reduces the levels of dissolved minerals down to an acceptable level for potable water
  • you can use distillation
  • or to pass water through membranes using reverse osmosis
  • however these processes use a lot of energy making them very expensive
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6
Q

What are artificial fertilisers?

A

Allows us to grow more food with the land available.

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7
Q

What is waste water?

A

Contains a large amount of organic molecules such as from urine and faeces.

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8
Q

What are the steps in waste water treatment?

A
  1. the sewage is screened by passing it through a mesh.
    - this removes solids and pieces of grit
  2. Now sewage can settle in large sedimentation tanks.
    - this produces a liquid effluent and a semi-sloid sludge which sinks
  3. The sludge is taken away and digested by the anaerobic bacteria.
    - in the absence of oxygen, these bacteria produce biogas which can be burned for electricity
  4. The digested sludge can be used as fertilisers for farming
  5. The liquid effluent contains large amounts of organic molecules and harmful organisms.
  6. Air is bubbled through the liquid effluent, allowing aerobic bacteria to multiply.
    - in the presence of oxygen, the aerobic bacteria digest the organic molecules and harmful microorganisms
  7. The liquid effluent can be safely discharged into nearby river/seas.
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9
Q

Why is potable water not regularly produced from waste water?

A
  • many purification steps

- only done where water is scarce

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10
Q

What is desalination used for and what is its disadvantage?

A
  • salt water

- requires lots of energy and it is expensive

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11
Q

What is problem with copper ore running out?

A
  • we will have to extract copper from low-grade ores
  • these only contain small amounts of copper
  • so it is harder to extract economically
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12
Q

Name alternative methods of extraction

A

Phytomining

Bioleaching

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13
Q

What is phytomining?

A
  1. Plants are grown on land containing the metal compound that we want (low grade copper ore)
  2. These plants absorb the metal compound and concentrate it in their tissue
  3. Plants are then harvested and burned
  4. The ash contains a relatively high concentration of the metal compound
  5. It is then extracted using displacement/electrolysis
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14
Q

What is bioleaching?

A
  1. Bacteria are mixed with a low-grade ore

2. The bacteria carry out chemical reactions and produce a solution of metal ions called leachate.

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15
Q

Why are copper compounds displaced using iron?

A

Iron is more reactive than copper

And scrap iron is cheap

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16
Q

What are the advantages of the alternative methods of extraction?

A
  • allows us to economically extract metals from low-grade ores.
  • does not involve digging, transporting and disposing of large amounts of rock like in traditional mining
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17
Q

What is a life-cycle assessment?

A

It attempts to put a number on the environmental impact of a product.

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18
Q

Advantages and disadvantages of plastic bags:

A

Advantage:
-strong so often reused

Disadvantages:

  • produced using chemicals from crude oil- non-renewable and harmful to habitats e.g. oil leaks
  • crude oil needs to be chemically processed which needs a large amount of energy and creates lots of waste products
  • plastic is non-biodegradable as it is not broken down by microorganisms- so it remains in the environment for a very long time and fills up landfills
19
Q

Advantages and disadvantages of paper bags:

A

Advantages:

  • made from wood from trees -they are renewable as you can just plant more
  • paper breaks down quickly, especially when wet, so it doesn’t stay in the environment for a long time

Disadvantages:

  • wood needs to be chemically processed which uses a large amount of energy and creates lots of waste products
  • felling trees for wood is extremely destructive for habitats
  • they aren’t strong as they tear quickly, can’t be reused
  • making paper requires a large amount of water-harmful for habitats
20
Q

What is the problem with life-cycle assessments?

A
  • judgements and estimates may not be accurate
  • we cannot be certain of how much damage is being done to the environment
  • can be biased e.g. to support claims made by advertisers
21
Q

What are the advantages of recycling?

A
  • saves limited resources and energy
  • less mining and quarrying that destroys the habitat
  • reduces the amount of waste we produce
  • less harmful on the environment
22
Q

What is corrosion?

A

The destruction of materials by chemical reactions with substances in the environment e.g. rusting.

23
Q

Describe an experiment on the conditions required for rusting:

A 
Test Tube 1: (water + air)
-iron nail in distilled water
-test tube is open to air
Test Tube 2: (water, no air)
-iron nail in distilled water
-water has been boiled
-this removes any dissolved air
-water covered by oil
-prevents any air in the test tube from dissolving in water
Test Tube 3: (air, no water)
-anhydrous calcium chloride powder
-this removes any water from the air in the test tube
-rubber bung prevents moist air from entering

Leaves these for several days.

  • test tube 1, the iron nail is covered in rust
  • test tube 2 and 3 there is no rust
  • therefore rusting requires both air and water
24
Q

Stopping corrosion:

A
  • grease
  • paint
  • electroplating
  • sacrificial protection
25
Q

What is electroplating?

A

Coating the material with a metal e.g. aluminium oxide

26
Q

What is sacrificial protection?

A
  • coating with a more reactive metal

e. g. zinc is used to galvanise iron

27
Q

What is an alloy?

A

A mixture of a metal blended with other elements. Tend to be harder.

28
Q

How are alloys made?

A
  • melting the metal
  • mixing in other elements
  • allowing it to cool
29
Q

Compare alloys and pure metals

A 
Pure metals:
-atoms can form layers
-which can slide over each other
-relatively soft
Alloys:
-atoms are different sizes
-disrupts/distorts the layers and stops them from sliding
-alloys are harder
30
Q

Bronze:

A
  • alloy of copper and tin
  • extremely hard and doesn’t corrode
  • used in statues
31
Q

Brass:

A
  • alloy of copper and zinc
  • harder than pure metal but can still be formed into different shapes
  • used for musical instruments and door handles
32
Q

Gold:

A
  • alloyed with sliver, copper, zinc to make it harder
  • 24 carat: 100% pure gold
  • 18 carat: 75% gold
  • 12 carat: 50% gold
33
Q

Steels:

A
  • these are alloys of iron containing specific amounts of carbon
  • also contains other metals

High carbon steel:

  • extremely hard
  • brittle
  • used in cutting tools

Low carbon steels:

  • softer and more easily shaped
  • used to make car bodies

Stainless steel:

  • contains chromium and nickel to prevent rusting along with iron and carbon
  • hard and resistant to corrosion
34
Q

Aluminium alloys:

A
  • low density

- useful in aeroplane bodies

35
Q

Give two examples of glass ceramics:

A

Soda-lime glass

Borosilicate glass

36
Q

What is soda-lime glass used for and how is it made?

A
  • ideal for windows and bottles
  • mix together sand, sodium carbonate and limestone
  • heat the mixture in a furnace until it melts
  • when it cools, it solidifies into any shape that we want
37
Q

What is the problem with soda-lime glass?

A
  • relatively low melting point

- limits its uses

38
Q

Borosilicate glass:

A
  • higher melting point than soda-lime glass
  • useful for objects that require heating
  • made by melting a mixture of sand and boron trioxide
39
Q

Clay ceramics?

A
  • clay is a mineral that can be found in the ground
  • can be shaped when wet
  • then heated in a furnace to harden
40
Q

What are composites?

A
  • they are made by combining two different materials
  • reinforcement (fibres of fragments of one material) which is surrounded by a matrix or binder material
  • composites have different properties to the materials in them
41
Q

Carbon fibre composite:

A

Reinforcement material: fibres of carbon
Matrix: plastic resin
-very strong and light
-useful in cars and aircraft parts

42
Q

Reinforced concrete:

A
  • steel bars surrounded by concrete
  • extremely strong
  • used to make buildings
43
Q

Thermosoftening polymers:

A
  • melt when we heat them
  • we can reshape them when they are soft
  • they go back to solid when we cool them down

Structure:

  • polymerchains are held together by intermolecular forces
  • forces break when heated
  • so polymer strands seperate from each other and polymer melts
44
Q

Thermosetting polymers:

A
  • do not melt when we heat them
  • polymer chains are connected by strong crosslinks
  • these aren’t broken by heat
  • so the polymers don’t seperate when heated

Chemistry Paper 2 (5 decks)

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