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Chemistry Paper 2 > C14 The Earth's resources > Flashcards

C14 The Earth's resources Flashcards

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1
Q

What is sustainability?

A

Using resources to meet the needs of society now, without endangering the ability of future generations to meet their needs

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2
Q

Explain how potable water is produced from fresh water

A
  • Fresh water is collected from an appropriate source such as rivers, streams or lakes
  • The water is passed through filter beds, usually made of sand and gravel, which removes undissolved solids
  • The water is sterilised using chlorine, but sometimes ozone or UV light, which destroys harmful microbes
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3
Q

What is an ore?

A

A rock which contains enough metal to make it economically worthwhile to extract the metal

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4
Q

describe the properties of copper

A
  • Unreactive so corrosion resistant
  • Very good conductor of heat and electricity
  • High melting point
  • Malleable and ductile
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5
Q

Uses of copper

A
  • Electrical wiring
  • Gas and water pipes
  • Sauce pan bases
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6
Q

How could you extract copper from its ore?

A

Reduction by carbon

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7
Q

Explain how phytomining works

A
  • Plants grow on soil contains low-grade copper ore
  • Plants take up copper from the soil by their roots
  • Plants are burnt and the ash dissolved in sulphuric acid to produce copper sulphate
  • Copper displaced by adding iron
  • Impure copper purified using electrolysis
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8
Q

Explain how bioleaching works

A
  • Bacteria feed on low-grade copper ores
  • Through biological and chemical processes, a solution of copper ions is produced
  • Copper is displaced by adding iron
  • Impure copper is purified using electrolysis
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9
Q

Traditional methods of extracting copper

A

Smelting
- copper ore is heated to high temperature in a furnace to produce impure copper

Sulphuric acid
- copper can also be extracted using sulphuric acid to produce copper sulphate
- the copper can then be extracted via a displacement reaction

Impure copper is then electrolysed to produce pure copper

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10
Q

Explain the electrolysis of impure copper

A
  • Impure copper is used for the anode
  • Pure copper is used for the cathode
  • Uses copper sulfate solution
  • At the anode, copper atoms from impure copper are oxidised to copper ions
  • Copper ions transported from anode to cathode
  • At the cathode, copper ions from impure copper are reduced to copper atoms
  • As the atoms of the impurities are not transported, the copper that builds up on the cathode is extremely pure
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11
Q

Problems of traditional methods of extracting copper

A

Mining:
- produces large amounts of waste rock
- destroys habitats
- scars the landscape

Smelting:
- requires lots of energy for smelting and then electrolysis
- only worth extracting from high-grade ores which are finite resources

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12
Q

What is meant by a high-grade ore?

A

Rock that contains a high percentage of metal

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13
Q

What is meant by a low-grade ore?

A

Rock that contains a low percentage of metal

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14
Q

Advantages of bioleaching

A
  • Very energy efficient
  • Simple process than smelting, which requires fewer expert staff to operate, reducing costs
  • Used to extract copper from low grade ores which are unsuitable for smelting
  • Produces less sulphur dioxide emissions than smelting
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15
Q

Disadvantages of bioleaching

A
  • It is very slow, takes a long time for companies to earn money from their investment in a bioleaching business
  • The process can produce toxic chemicals which may run off into rivers and other sources of drinking water
  • Once started, the process can take a long time to stop should a pollution problem arise
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16
Q

Advantages of phytomining

A
  • Decontaminates polluted ground
  • Obtain metal from ground where other extraction methods would not be suitable
  • Carbon emissions are lower than for smelting
17
Q

Disadvantages of phytomining

A
  • Copper produced isn’t pure and requires electrolysis, so it is not energy efficient
  • Growing high yielding plants reduces nutrients in the soil and may require a high input of fertilisers to maintain growth
  • The concentration of metals in plants is very low
  • It is dependent on good growing conditions such as adequate rainfall
18
Q

What is phytomining?

A

The extraction of copper from low-grade copper ore, using plants

19
Q

What is bioleaching?

A

The extraction of copper from low-grade ores, using bacteria

20
Q

Similarities between phytomining and bioleaching

A
  • Both methods produce a solution of metal compounds, more concentrated than they were in the low-grade ore
  • The metal compounds can be processed to obtain the metal, by displacement reaction with iron and/or by electrolysis
21
Q

Environmental impacts of the production, usage and disposal of Lego

A
  • Packaged in cardboard boxes and plastic bags, plastic comes from crude oil
  • Transported around the world, ships and lorries use fossil fuels
  • Lego cannot be recycled, most goes to landfill
  • Heat is used to melt the plastic so it can be moulded into shape, much of this energy comes from burning fossil fuels, leads to pollution
22
Q

What are life cycle assessments?

A

Used to assess the impact on the environment caused by manufactured goods at each stage of their life (from cradle to grave)

23
Q

What are the four stages that need to be considered when carrying out LCAs?

A
  • Extract and process raw materials
  • Manufacturing and packaging
  • Use and reuse of product
  • Disposal of the produce at the end of its useful ‘life’
24
Q

How is a LCA carried out?

A
  • Listing all the energy and material inputs and outputs to the environment
  • Inputs = raw materials, energy
  • Outputs = atmospheric emissions, waterborne wastes, solid wastes, coproducts
  • Evaluating the environmental impact of these inputs and outputs
  • Interpreting the results to make decisions about using one material, process, product to service over another
25
Q

Problems with LCAs

A
  • It is not easy to quantify the effects of pollutants, because we can’t be sure what the overall effect will be, this means we have to use value judgements
  • Value judgements are subjective
  • Because LCAs use a mix of numerical values and value judgements, LCAs are not a purely objective process
26
Q

What are the three R’s?

A
  • Reduce
  • Reuse
  • Recycle
27
Q

What things will the three R’s campaign reduce?

A
  • Our use of limited resources
  • Our use of energy
  • The amount of waste produced, landfill takes up space and pollutes the surroundings
28
Q

What is the aim of the reduce step and why is it needed?

A
  • Because both the materials and the energy sources are limited, we need to reduce use of the resources so they do not run out
  • Also, because obtaining raw materials from the Earth by quarrying and mining causes environmental impacts
29
Q

Environmental impacts of obtaining raw materials by mining and quarrying

A
  • Visual pollution
  • Noise
  • Destroys habitats
  • Water mixing with the metal ores in the ground can cause acidic water which pollutes water sources
  • Dust
30
Q

Why is it important to recycle glass?

A
  • Less energy needed to recycle compared to making new glass
  • Less pollution created through recycling
  • Less space needed for landfills
  • Less use of limited resources
31
Q

describe the treatment of waste water

A
  • screening: the water passes through a metal grid to remove large solids and grit
  • sedimentation: solid sediments are allowed to settle out from the mixture, heavier solids sink to the bottom creating sewage sludge, lighter matter known as effluent flows into the next tank
  • aerobic digestion: bacteria feed on any remaining organic matter and harmful microorganisms present, breaking them down aerobically, treated effluent is released back into rivers and lakes
  • anaerobic digestion: sewage sludge is digested anaerobically by microorganisms
32
Q

what happens to the products released during the breakdown of sewage sludge?

A
  • the breakdown products include biogas (a mixture of methane, carbon dioxide and some hydrogen sulphide)
  • biogas can be burned and used to power the sewage treatment plant or provide electricity for the surrounding area
  • anaerobic respiration releases methane which can be used as a fertiliser and a source of renewable energy

Chemistry Paper 2 (9 decks)

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