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CHEMISTRY > C14 The Earth's Resources > Flashcards

C14 The Earth's Resources Flashcards

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1
Q

What is the difference between potable and pure water?

A

Pure water contains no dissolved substances

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2
Q

What are the 2 main steps to produce drinking water from lakes?

A

Filtration - Removes large solids

Sterilisation - Remove microbes

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3
Q

Describe the steps to produce potable water

A
  • WATER COMES FROM A FRESH SOURCE (River, lake or reservoir)
  • Water is passed through a filter made of fine sand and gravel, removing any
    remaining particles of mud or grit, so the water is clean.
  • Water is passed through another filter, made with metal bar close together,
    to catch large objects such as leaves and twigs
  • Water reaches a settlement tank, where sand and soil settle out
  • Aluminium sulfate and lime are added to the water, small particles of dirt
    clump together and sink to the bottom of the water
  • Chlorine added to kill bacteria (Or Ozone or UV light)
  • pH of water checked to be neutral + sludge dumped in landfill
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4
Q

What is required to produce potable water?

A

A fresh water source e.g. a river, lake or reservoir

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5
Q

What method is used to produce potable water from salty water?

A

Desalination (Reducing amount of dissolved minerals in water)

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6
Q

Describe two methods of desalination

A
  • Distillation

- Passing the water through a membrane (Reverse osmosis)

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7
Q

What is a disadvantage to methods of desalination?

A

They require a lot of energy, and are therefore expensive

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8
Q

What does it mean if a resource is finite?

A

It can’t be replaced as quickly as it’s being used

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9
Q

Name 2 finite resources

A

Metals and Fossil fuels

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10
Q

What do we use resources to provide?

A

Warmth, Shelter, Food and Transport

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11
Q

Describe a resource that is produced from farming

A

Cotton - Produced from a plant

Timber/ Fuel - Produced from trees

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12
Q

Describe a natural resource that has been replaced with a synthetic alternative

A

Rubber - Natural rubber comes from the sap of a tree, however synthetic rubber is produced using crude oil

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13
Q

Describe how waste water is treated

A
  • Sewage passes through a mesh, removing solids and grit
  • Sewage settles in sedimentation tank, producing a liquid effluent and
    sludge, which is taken away and digested by anaerobic bacteria
  • Digested sludge can be used as fertiliser for farming
  • Air is bubbled through the water to increase digestion from aerobic bacteria
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14
Q

Why is anaerobic bacteria used to digest waste sludge in wotar?

A

It produced biogas, which can be burnt to produce energy

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15
Q

Why is air bubbled through the water during waste treatment?

A

It allows aerobic bacteria to multiply, which digest harmful organic molecules and microorganisms

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16
Q

Describe the easiest to hardest ways of producing potable water

A
  • Ground water from aquifers (usually safe once treated with CL)
  • From waste water (Takes many purification steps)
  • From salt water (Requires a lot of energy and is expensive)
17
Q

What is one risk associated with extracting water from aquifers?

A

They may be polluted e.g. with fertilisers from farms

18
Q

How are raw materials usually obtained?

A

Quarrying or mining

19
Q

Describe the disadvantages of quarrying and mining

A

Quarrying - Produced large amounts of dust and destroys habitats
Mining - Releases harmful chemicals into the environment

(Also requires a lot of energy which comes from fossil fuels)

20
Q

Describe how glass bottles can be reused

A

They can be crushed and melted to form new products

21
Q

How are metals recycled?

Give a disadvantage

A

By being melted and recasted into new products

Different metals need to be separated before being recycled

22
Q

Describe how plastics can be recycled?

A

They can be recycled to make fleece jackets and carpets

23
Q

Describe an LCA for a plastic bag and a paper bag

A

PLASTIC
- Produced using chemicals from crude oil (finite resource)
- Extracting crude oil can be harmful to habitats (releasing chemicals)
- Oil must be chemically processed (requires energy + releases waste)
- Plastic bags are strong and can be reused
- Must be transported (for recycling or landfill) which requires energy
- Plastic is NON BIODEGRADABLE, and remain in the environment for a long
time

PAPER

  • Produced using trees, which are a renewable resource
  • Cutting down trees is extremely disruptive to habitats e.g. forests
  • Wood must also be chemically process
  • Making paper also requires a large amount of water
  • Paper bags aren’t as strong and tend to tear (Only used once)
  • Paper bags are often heavier than plastic bags (more energy to transport)
  • Paper breaks down quickly, especially when wet
24
Q

Plastic is non biodegradable, what does this mean?

A

It isn’t broken down by microorganisms

25
Q

What is an issue with LCA’s?

A

We cannot be certain how damaging each product is to the environment, so in some cases, some estimates/ value judgements must be made, and may not always be accurate

Also they could be biased to support claims made by advertisers

26
Q

Seawater is forced though a membrane to produce freshwater, suggest why water molecules can pass through the membrane but not sodium or chlorine ions

A
  • Water molecules have no overall charge

- Na+ and Cl- ions are larger

27
Q

Suggest 3 reasons why copper shouldn’t be disposed of in landfill sites

A
  • Copper can be recycled/reused
  • Copper compounds are toxic
  • Copper is running out
  • Copper is expensive
  • Landfill sites are filling up
28
Q

Suggest 3 reasons why world production of coal is predicted to increase

A
  • Plentiful supply
  • Easier to extract
  • Oil/gas is running out
    (Oil is a limited resource)
29
Q

What is in water filters that removes hardness from water?

A

Ion exchange resin

30
Q

Suggest why water filters in homes contain particles of silver

A

Prevents growth of microbes

31
Q

Describe how phytomining can be used to extract copper

A
  • Plants grown on land containing desired compound
  • Plants absorb metal (copper) compound and concentrate it in its tissue
  • Plants are harvested and burnt
  • Ash contains relatively high concentration of metal compound

(extract with iron or electrolysis)

32
Q

Describe how bioleaching can be used to extract copper

A
  • Bacteria is mixed with low grade ore
  • Bacteria carry out chemical reactions and produce a solution called a LEACHATE
  • Leachate contains desired metal compound
  • Extract copper from metal compound using displacement with iron
    (iron is cheap)
33
Q

What are the benefits of alternate methods of extracting metals?

A
  • Don’t involve digging/quarrying etc

- Help to economically extract low grade ores

CHEMISTRY (18 decks)

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