C14 The Earth's Resources

Question 1

what are the Earth’s resources used for?

Answer 1

food
shelter
transport
warmth

Question 2

in most cases, how are the resources that humans use produced?

Answer 2

agriculture

Question 3

what can trees be used for?

Answer 3

timber
fuel

Question 4

what does finite mean?

Answer 4

a resource that cannot be replaced as quickly as it is being used

Question 5

what are some finite resources?

Answer 5

metals
fossil fuels

Question 6

what does renewable mean?

Answer 6

a resource that can be replaced as quickly as it is used

Question 7

what does potable water mean?

Answer 7

water that is safe to drink
it is low in microbes and sufficiently low levels of dissolved salts

Question 8

what is pure water?

Answer 8

it contains just water molecules
there are no dissolved substances

Question 9

how is potable water produced?

Answer 9

• choose a source of fresh water
• pass water through filter beds
• the water is then sterilised to kill microbes

Question 10

what can be used to sterilised water?

Answer 10

• chlorine
• ozone
• UV light

Question 11

what is desalination?

Answer 11

a process which reduces the levels of dissolved minerals to an acceptable level for potable water

Question 12

how is desalination carried out?

Answer 12

• distilation
• reverse osmosis

Question 13

why is desalination expensive?

Answer 13

both processes (distilation and reverse osmosis) require a lot of energy

Question 14

what is water used for?

Answer 14

• drinking
• personal hygiene
• agriculture
• flushing toilets
• washing clothes

Question 15

why does waste water have to be treated before going back into the environment?

Answer 15

it contains a large amount of organic molecules as well as harmful microbes

Question 16

what are the stages of waste water treatment?

Answer 16

• water is screened through a mesh to remove solids
• sewage settles in sedimentation tanks which produces an effluent and sludge
• sludge is digested by anaerobic bacteria
• air is bubbled through the liquid effluent to allow aerobic bacteria to multiply
• aerobic bacteria digest organic molecules and harmful microbes
• liquid effluent is then safely discharged into rivers or the sea

Question 17

what is produced in the anaerobic digestion of sludge?

Answer 17

biogas that is burned for electricity

Question 18

what can digested sewage sludge be used for?

Answer 18

fertilisers for farming

Question 19

what needs to be removed from water waste from industry?

Answer 19

harmful chemicals

Question 20

what is the easiest way to produce potable water?

Answer 20

to use ground water from aquifers treated with chlorine

Question 21

how is potable water produced when water is scarce?

Answer 21

directly from waste water which takes many purification steps

Question 22

what does salt water need to become potable water?

Answer 22

it needs to be desalinated

Question 23

why is copper an important metal?

Answer 23

it is used in electrical equipment

Question 24

why do we have to extract copper from low grade ores?

Answer 24

the high grade copper ores are running out

Question 25

how is phytomining carried out?

Answer 25

• plants are grown on the land containing the metal compound wanted
• the plants absorb the metal compound and concentrate it in their tissue
• plants are then harvested and burned
• the ash then contains a relatively high concentration of the metal compound

Question 26

what is bioleaching?

Answer 26

using bacteria to extract metals

Question 27

how is bioleaching carried out?

Answer 27

• bacteria are mixed with low grade ore
• bacteria carry out chemical reactions which produces a solution called leachate that contains the desired metal compound

Question 28

what happens at the end of phytomining and bioleaching?

Answer 28

the desired metal needs to be extracted
this can be done with displacement or electrolysis

Question 29

why is scrap iron used when extracting copper?

Answer 29

it is more reacive than copper and is cheap as it is scrap

Question 30

what are some advantages of phytomining and bioleaching?

Answer 30

• they allow metals to be economically extracted from low grade ores
• they do not involve digging, transporting and disposing of large amounts of rock

Question 31

what is a life cycle assessment?

Answer 31

carried out to assess the environmental impact of products, processes or services at different stages in their life cycle

Question 32

what are the stages in an LCA?

Answer 32

• raw material extraction
• manufacture
• use/reuse/mainenance
• recycle/waste management

Question 33

how is an LCA carried out?

Answer 33

• listing all energy and material inputs and outputs into the environment
• evaluate potential environmental impacts
• interpreting the results can help make decisions about using something

Question 34

what is wrong with LCAs?

Answer 34

numerical values are assigned to the relative effects of pollutants and involves subjective judgements

Question 35

what is the benefit of recycling metals?

Answer 35

it saves energy and the limited, finite metal ores
the pollution caused by mining and extraction is also reduced

Question 36

how much energy is saved when aluminium is recycled?

Answer 36

95%

Question 37

how much energy is saved when recycling steel?

Answer 37

50%

Question 38

why is it difficult to recycle copper?

Answer 38

copper is often alloyed with other metals so has to be purified