C14 - The Earth's resources

Question 1

What do we use resources for?

Answer 1

-food
-heating
-shelter
-transport

Question 2

What is the difference between pure and potable water?

Answer 2

-pure water is pure in the chemical sense, as it only contains H₂O

-potable water is water that is safe to drink, and has low levels of dissolved substances (meaning it is not pure)

Question 3

What does rainwater provide us with?

Answer 3

rainwater provides water with low levels of dissolved substances that collects in the ground/lakes/rivers (freshwater)

Question 4

How is potable water produced in the UK?

Answer 4

-an appropriate source of freshwater is chosen (eg rivers/lakes)
-the water is passed through filter beds (layers of clean sand/gravel) to remove undissolved solids
-it is then sterilised with either chlorine, ozone, or UV light, to destroy harmful microbes

Question 5

If you can’t produce water in the same way as the UK does, what other methods are there? Give a drawback to using them:

Answer 5

-desalination of sea water through either distillation, or reverse osmosis (forcing seawater through partially permeable membranes)

-requires lots of energy, and is very expensive

The image says "portable" water, when it should be potable

Question 6

The process of filtration does not change the concentration of sodium and chloride ions in water. Explain why:

Answer 6

-sodium and chlorine ions are dissolved in the water
-they are far too small to be removed by the filter, as the holes in the filter are too big

Whenever talking about ions in solution, mention the fact that they are dissolved

Question 7

Why is it necessary to use desalination to produce potable water in some places?

Answer 7

supplies of freshwater are limited

Question 8

RP8 - How could you analyse the mass of solids dissolved in a sample of water?

Answer 8

-record mass of empty evaporating basin
-add water sample
-heat with Bunsen burner until all water evaporates
-reweigh, and keep reheating it until a constant mass is obtained
-record mass of evaporating basin with solids left behind
-take difference to find mass of solids

Question 9

RP8 - How can you purify a sample of water? Describe the method:

Answer 9

-distillation

-pour water sample into conical flask and connect to a delivery tube and condenser, and at the other end of the tube, put a collection beaker
-heat water in flask with Bunsen burner until no water remains in the flask
-cold water around the condenser will condense the steam into pure water, which will be collected in the beaker

Question 10

Why do we need to treat waste water?

Answer 10

-sewage and agricultural waste water contains harmful microbes and organic matter
-industrial waste water contains harmful chemicals and organic matter

-they need to be treated before being released, as it severely damages the environment and health of organisms

Question 11

Name the steps involved in sewage treatment:

Answer 11

-screening and grit removal
-sedimentation in settlement tanks
-anaerobic bacteria to digest sludge
-aerobic bacteria to treat effluent

ALWAYS SAY THE BACTERIA

Question 12

Describe the process of screening sewage:

Answer 12

the waste water is passed through a mesh which will remove larger objects like twigs/bags

Question 13

Describe the process of sedimentation in sewage treatment:

Answer 13

-the screened waste water sits still in settlement tanks

-heavy solids to fall and produce sewage sludge
-lighter solids float to the top and produce effluent

Question 14

Describe the final step involved in sewage treatment:

Answer 14

anaerobic bacteria - digests the sludge, and produces methane for fuel, and leftover digested waste is used as a fertiliser

aerobic bacteria - treats the effluent which can then be returned to the environment

Always mention that there are (an)aerobic bacteria

Question 15

Explain why it is more difficult to produce potable water from waste water than from freshwater:

Answer 15

waste water needs many more different processes because it has more organic matter and microbes

Question 16

Name 2 methods of extracting metal compounds from low-grade ores:

Answer 16

-phytomining
-bioleaching

Question 17

Describe the process of phytomining:

Answer 17

-grow plants on land containing low-grade ores
-harvest and burn the plants to produce an ash
-dissolve the ash in acid to make a solution of the metal compounds
-perform electrolysis on the solution (or displacement reaction)

Question 18

Describe the process of bioleaching:

Answer 18

bacteria is used to produce leachate solutions that contain metal compounds

Leachate is water that has percolated through a solid (eg mud)

Question 19

How can low-grade ores be treated after extraction in order to remove the metal?

Answer 19

the ore compounds get processed with displacement reactions (eg extract copper from solution with scrap iron) or electrolysis

Question 20

Why might copper now be extracted from low-grade ores?

Answer 20

-high-grade copper ores are running out
-it is now economically viable to extract copper from low-grade ores due to newer methods like phytomining and bioleaching

Question 21

What is an LCA?

Answer 21

a life cycle assessment, which is performed to assess the environmental impact of a product at 4 stages of their lifetime

Question 22

What stages of a product’s life cycle does the LCA assess?

Answer 22

-extraction/processing of its raw materials
-manufacturing and packaging
-usage during the product’s lifetime
-disposal after its usage

-transport/distribution at all 4 of the stages above

Question 23

Why aren’t LCAs always accurate?

Answer 23

-exact numerical values can’t always be placed on certain aspects (eg a pollutant’s effects on the environment)
-this means LCAs aren’t always purely objective

Question 24

How can LCAs be misused?

Answer 24

selective/abbreviated LCAs can be misused to reach pre-determined conclusions (eg being in support of advertisement claims)

Question 25

How can we reduce the consumption of resources?

Answer 25

recycle or reuse a product at the end of its life

Question 26

What effect does reusing and recycling products have?

Answer 26

reduces:
-use of limited resources
-energy consumption
-production of waste and their environmental impacts

Question 27

Name some products that are obtained from limited raw materials:

Answer 27

metals, glass, clay, ceramics, plastics, building materials

Question 28

How can glass be reused?

Answer 28

crush it, melt it, and use it to make other glass products

Question 29

How can metals be recycled? Name the factors that affect how it is recycled:

Answer 29

-melt/recast/reform the metal into different products

-depends on the material being recycled and the properties required in the final product

Question 30

Aluminium is obtained from aluminium oxide, and carbon is obtained by heating coal. Why is aluminium more expensive than carbon?

Answer 30

-aluminium is very expensive to extract from its oxide (requires electrolysis)
-uses much more energy to supply the current to perform electrolysis and to melt the oxide, rather than just heating the coal

Question 31

Suggest why we should recycle aluminium cans, even if aluminium is one of the most abundant metals in the Earth’s crust:

Answer 31

-to save resources as aluminium is non-renewable
-less mining, so it saves energy and reduces emissions (give a specific type, eg carbon dioxide)