Ch14 The Earth's resources

Question 1

Potable water

Answer 1

water that is safe to drink

contains useful dissolved substances(not pure)

Question 2

Obtaining fresh water

Answer 2

Rainwater falls to the ground
replenishes water in rivers and lakes
also seeps through soil and rocks to underground sources(aquifers)
can be obtained from porous rocks by drilling a pipe to form a water well

Question 3

Forming potable water

Answer 3

1. choose an appropriate source of fresh water
2. pass the water through filter beds made of sand and gravel to remove solid particles
3. a. sterilise the water by adding chemical agents such as chlorine or ozone, killing microorganisms
   b. sterilise the water by passing ultraviolet light through the water, killing microorganisms

Question 4

Desalination methods

Answer 4

1. distillation

2. reverse osmosis

Question 5

Advantages of distillation

Answer 5

under reduced pressure, water boils below 100°C (flash distillation) saving energy costs

Question 6

Disadvantages of distillation

Answer 6

expensive

takes lots of energy

Question 7

Reverse osmosis

Answer 7

Water is put under high pressure and passed through a partially permeable membrane
-has tiny pores (holes) in it, allowing water molecules through, but preventing most ions and molecules

Question 8

Advantages of reverse osmosis

Answer 8

No heating involved, so it uses less energy than distillation
removes 98% of dissolved salts

Question 9

Disadvantages of reverse osmosis

Answer 9

corrosion of pumps by salty water

lots of energy is needed to pressurise the water passing through

Question 10

Finite resources

Answer 10

Those being used at a faster rate than they can be replaced

Question 11

Examples of finite resources

Answer 11

fossil fuels
nuclear fuels
metal ores
limestone

Question 12

Renewable resources

Answer 12

Those that can be replaced at the same rate at which they are used up

Question 13

Examples of renewable resources

Answer 13

crops used to make biofuels

wind

water

Question 14

Sustainable development

Answer 14

development that meets the needs of current
generations without compromising the ability of future generations
to meet their own needs

Question 15

Examples of using lower amounts of finite resources

Answer 15

catalysts reduce the amount of energy required for certain industrial processes

man-made polymers can replace rubber extracted from tree sap

Question 16

Sewage treatment

Answer 16

1. screening - removing large solid objects and grit
2. sedimentation to produce sewage sludge and effluent
3. aerobic biological treatment of effluent
   - useful bacteria feed on any remaining organic matter and harmful microorganisms
4. can be sterilised by ultraviolet light or chlorine, then discharged back into rivers
5. anaerobic digestion of sewage sludge in high temperatures
6. sewage dries, producing fertiliser, biogas or biofuel

Question 17

Extracting copper metal from copper-rich ores

Answer 17

1. sulfuric acid is used to produce copper sulphate solution

2. smelting - copper ore is heated to a high temp in a furnace with air to produce impure copper

Question 18

Making pure copper from impure copper

Answer 18

1. electrolysis

2. copper can be displaced from copper sulphate by iron

Question 19

Bioleaching

Answer 19

bacteria feed on low-grade metal ores

produces acidic leachate solution containing copper(II) ions

Question 20

Phytomining

Answer 20

plants absorb copper ions when growing on soil containing low-grade copper ore
plants are harvested and then burned to produce ash that contains copper compounds
copper ions are then leached/dissolved from the ash by adding sulfuric acid to make copper sulphate

Question 21

Life cycle assessments

Answer 21

used to assess the impact on the environment caused by:
1. extracting and processing the raw materials
2. manufacturing and packaging
3. using, reusing and maintaining the product
during its lifetime
4. disposal of the product at the end of its useful life, including transport and
distribution at each stage

Question 22

Extracting raw materials impact on the environment

Answer 22

using up limited resources such as ores and crude oil

damaging habitats through quarrying, mining, or felling trees

Question 23

Manufacturing impact on the environment

Answer 23

using up land for factories

the use of machines and people

Question 24

Disposal impact on the environment

Answer 24

using up land for landfill sites

whether any or all of the product can be recycled or reused