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AQA Chemistry > Using Resources > Flashcards

Using Resources Flashcards

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1
Q

why do we use resources?

A

they provide food, shelter, warmth and transport

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2
Q

finite vs natural resources

A
  • natural resources supplemented by agriculture=provide food,
    timber, clothing and fuels
  • finite resources
    from the Earth, oceans and atmosphere=processed to provide energy and materials
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3
Q

pure vs potable water

A

pure water only contains H2O molecules
potable water is safe to drink and contains low levels of dissolved salts

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4
Q

how is potable water made?

A
  • choosing a fresh water source
  • passing water through filter beds=removes large solids
  • sterilising with chlorine, UV, ozone to get rid of any microbes
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5
Q

how is potable water made without freshwater?

A

desalination through distillation or reverse osmosis (any process using membranes) which require energy=expensive

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6
Q

required practical: water purification

A
  1. Use universal indicator to test the pH of 10 ml rainwater, spring water, sea water
  2. Measure and record the mass of an empty evaporating basin.
  3. Pour 10 cm3 of rainwater into the evaporating basin and evaporate the water using a bunsen burner
  4. let the basin cool and reweigh and record the change in mass
  5. Calculate the mass of dissolved solids in the water

OR

  1. Place the water sample in a conical flask and set up the apparatus for distillation.
  2. Heat the water gently using a bunsen burner until it boils. Then reduce the heat so the
    water boils gently.
  3. Collect around 1 cm depth of water in the cooled test tube, then stop turn the bunsen burner off
  4. Analyse the water you have distilled with cobalt chloride paper.
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7
Q

where does waste water come from?

A
  • urban lifestyles eg. going to the toilet
  • industrial processes eg. haber process
  • sewage from domestic/agricultural sources
  • agricultural waste
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8
Q

how is waste water treated?

A

Sewage treatment includes:
* screening and grit removal
* sedimentation to produce sewage sludge (suspended sediments) and effluent
* sludge rest at the bottom and effluent floats at the top
* anaerobic digestion of sewage sludge= CH4 released used as energy & rest of digested waste used as fertiliser
* aerobic biological treatment of effluent=bacteria break down organic matter
- waste water with toxic substances needs more steps to be treated eg. adding chemicals to precipitate metals, UV or using membranes

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9
Q

why do we need different ways of obtaining metals?

A
  • Copper ores are becoming scarce and new ways of extracting
    copper from low-grade ores include phytomining, and bioleaching
  • These methods avoid traditional mining methods of digging, moving
    and disposing of large amounts of rock.
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10
Q

what are other ways of extracting metals?

A

phytomining
- plants to absorb metal compounds
- plants are harvested and then burned to produce ash that contains metal compounds

bioleaching
- bacteria to produce leachate solutions (acid+metal solutions) that contain metal compounds.
- metal compounds can be processed to obtain the metal eg. copper can be obtained from solutions of copper
compounds by displacement using scrap iron or by electrolysis.

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11
Q

what is a life cycle assessment (LCA)?

A

they assess the environmental impact of products in each of these stages:
* 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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12
Q

problems with LCAs

A
  • use of water, resources, energy sources and production of some
    wastes can be fairly easily quantified
  • allocating numerical values to
    pollutant effects is less straightforward and requires value judgements=LCA is not purely objective
  • selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg
    in support of claims for advertising purposes.
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13
Q

how can the use of resources be reduced?

A
  • glass bottles can be reused
    Glass bottles=crushed and melted to make different glass products
  • metals can be recycled by melting and recasting or reforming into different products
  • amount of separation required for recycling depends on the material and the properties required of the final
    product eg. scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore
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14
Q

benefits of recycling metals

A
  • saves finite metal
  • less energy
  • less waste in landfill
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15
Q

what is corrosion?

A

destruction of materials by chemical reactions with
substances in the environment

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16
Q

what is rusting?

A

a type of corrosion, specific to iron

17
Q

what does iron need to rust?

A

air AND water

18
Q

how can corrosion be prevented?

A
  • applying a coating that acts as a barrier eg. greasing, painting or electroplating (aluminium has
    an oxide coating that protects the metal from corrosion)
  • Some coatings are reactive and contain a more reactive metal to
    provide sacrificial protection, eg zinc is used to galvanise iron=zinc more reactive=reacts with water and air instead of iron
19
Q

what is glass made of?

A
  • soda-lime glass=made by heating a mixture of limestone, sand and sodium carbonate (soda) till it melts=cools+forms glass
  • borosilicate glass=higher mp than soda-lime glass, made using a mixture of sand and boron trioxide
19
Q

how can we test rusting?

A
  • put an iron nail in a test tube with boiled water and oil to prevent air getting in
  • put an iron nail in a test tube with just air and calcium chloride which absorbs any water in the air
  • put an iron iron nail in a test tube with water and air=rusts
19
Q

how are alloys useful?

A
  • bronze is an alloy of copper and tin.
  • brass is an alloy of copper and
    zinc.
  • gold jewellery is an alloy with silver, copper and zinc
  • proportion of gold in the alloy is measured in carats:
    24 carat being 100% (pure gold), and 18 carat being 75% gold
    -steels=alloys of iron that contain specific amounts of carbon and other metals. High carbon steel is strong but brittle. Low carbon
    steel is softer and more easily shaped. Steels containing chromium and nickel (stainless steels) are hard and resistant to corrosion
  • aluminium alloys are low density
19
Q

how are composites made?

A
  • one material embedded in another
  • fibres/fragments of a material are surrounded by a matrix acting as a binder
    eg. fibreglass=glass fibres in a matrix of polymer, low density but very strong, used in skis, boats, surfboards
    carbon fiber composites= reinforcement made from longs chains of carbon atoms (carbon fibres) or carbon nanotubes, very strong and light, used in aerospace, sports car manufacturing
    Concrete=made from aggregate, embedded in cement, very strong, building materials
    Wood=natural composite of cellulose fibres held together by an organic polymer mix
19
Q

what are ceramics?

A

Non-metal solids with high mp that aren’t made of carbon based compounds eg. some are made from clay (pottery and bricks) and glass

20
Q

properties of polyethene

A

LDPE
- made with ethene at moderate temp+high pressure
- flexible
- used for bags and bottles (single use)
HDPE
- made from ethene at low temp+pressure and catalyst
- more rigid
- used for water tanks+drainpipes

20
Q

properties of thermo polymers

A

Thermosoftening
- contain individual polymer chains entwined together with weak forces between chains
- can melt and remould
Thermosetting
- contain monomers that can form cross links between polymer chains=holds chains in solid structure
- x soften when heated
- strong, hard, rigid

20
Q

the haber process

A

Ammonia is manufactured using the Haber Process which occurs in five stages
The reactants are hydrogen and nitrogen which are extracted from methane and the air respectively
Stage 1: H2 and N2 gases are pumped into the compressor through pipes
Stage 2: The gases are compressed to about 200 atmospheres inside the compressor
Stage 3: The pressurised gases are pumped into a tank containing layers of catalytic iron beads at a temperature of 450°C. Some of the hydrogen and nitrogen react to form ammonia in the following reversible reaction:
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

Stage 4: Unreacted H2 and N2 and product ammonia pass into a cooling tank. The ammonia is liquefied and removed to pressurised storage vessels
Stage 5: The unreacted H2 and N2 gases are recycled back into the system

21
Q

NPK fertlisers

A

Compounds containing nitrogen, potassium and phosphorus are used as fertilisers to increase crop yields
NPK fertilisers are formulations containing appropriate ratios of all three elements
From these three essential elements:
Nitrogen promotes healthy leaves,
Potassium promotes growth, healthy fruit and flowers
Phosphorus promotes healthy roots
A distinct advantage of artificial fertilisers is that they can be designed for specific needs whereas in natural fertilizers, such seaweed or manure, the proportions of elements cannot be controlled
Fertiliser compounds contain the following water soluble ions:
Ammonium ions, NH4+ and nitrate ions, NO3–, which are sources of soluble nitrogen
Phosphate ions, PO43-, which are a source of soluble phosphorus
Most common potassium compounds dissolve in water to produce potassium ions, K+

22
Q

Uses of ammonia

A

Ammonia is an alkaline substance and neutralises acids producing a salt and water
The salt it produces contains the ammonium ion, NH4+, which is a component of several fertilisers
Ammonia also undergoes oxidation to produce nitric acid, HNO3
Nitric acid is used as the source of the nitrate ion, NO3–, which is another important ion found in fertilisers
Ammonium nitrate, a fertiliser and one of the most important ammonium salts, is made by reacting ammonia with nitric acid:
NH3 (aq) + HNO3 (aq) → NH4NO3 (aq)

It is prepared on large scale industrial proportions but can also be prepared in the laboratory using a different method
In the laboratory it is prepared by titrating ammonia with sulfuric acid:
2NH3 (aq) + H2SO4 (aq) → (NH4)2SO4 (aq)

23
Q

How are phosphorus and potassium mined?

A

The Earth’s crust also contains useful minerals which are useful raw materials for making fertilisers
Phosphate rocks contain potassium chloride and potassium sulfate as they provide potassium
The rock itself is insoluble in water to it is usually reacted with acid to produce useful compounds with water soluble compounds:
With nitric acid, phosphoric acid and calcium nitrate are produced
The phosphoric acid is neutralised with ammonia forming ammonium phosphate
With sulfuric acid, a mixture of calcium phosphate and calcium sulfate is produced - this is know as single superphosphate
With phosphoric acid, calcium phosphate is produced - this is known as triple superphosphate

AQA Chemistry (10 decks)

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