C14

Question 1

What is pure water?

Answer 1

Water that contains only water molecules

Question 2

What is potable water?

Answer 2

Water safe to drink. It is not pure as it contains dissolved substances

Question 3

How do you treat fresh water?

Answer 3

1. filter out debris, let large dirt settle to the bottom
2. sterilise with chlorine, ozone or UV light

Question 4

How do you treat salt water?

Answer 4

1. filter out debris
2. desalinate (remove salt) by either distillation (high temp) or reverse osmosis (high pressure)

Question 5

what is the process of treating wastewater?

Answer 5

1. screening and grit removal to remove large particles
2. sedimentation allows tiny particles to settle out from still water, which produces sewage sludge and effluent (the liquid which remains on top)
3. the sewage sludge is digested anaerobically by specific bacteria
4. the effluent is treated with aerobic bacteria to reduce the volume of solid waste
5. Then sterilised and clean water goes into the river

Question 5

compare the treatments of fresh and salt water

Answer 5

fresh: cheaper, less energy used, quicker to process
salt: expensive as high temp and pressure use a lot of energy, salt corrodes (wears down) pumps

Question 6

describe the process of distillation (in desalination)

Answer 6

Sea water is heated until it boils. The salt remains in the liquid, and the steam is pure water. The steam is cooled and condensed to make potable water. (done by distillation)

Question 7

describe the process of reverse osmosis (in desalination)

Answer 7

Water is put under high pressure and passed through a
membrane which has tiny pores (holes) in it. The pores allow water molecules through, but prevent most ions and molecules from passing through

Question 8

What are the problems of distillation?

Answer 8

requires a lot of energy to boil the water, and also to cool the steam down to condense it. The waste water is very salty and can be difficult to dispose of in a
sustainable way which does not harm marine ecosystems

Question 9

What are the problems of reverse osmosis?

Answer 9

requires expensive membranes and also produces a large volume of waste water, so its
efficiency is often quite low.

Question 10

what’s sustainable development?

Answer 10

• meets the needs of current generations without compromising ability of future generations to meet their needs

Question 11

What are synthetic products, and what are some examples?

Answer 11

• man-made materials which replace or supplement natural resources

instead of wool, polymer (polyester)
instead of rubber, polymer

Question 12

If asked to “devise a fair test on a 100cm3 sample of water”, you must:

Answer 12

1. divide sample into smaller volumes to see if results are reproducible
2. always record the mass of any evaporating dishes before and after heating to calculate the difference
3. always use clean, dry equipment

Question 13

pH analysis of RP:

Answer 13

• low pH = acid rain or distilled water
• high pH = water from carbonate rocks/dissolved minerals.
• Pure water = pH7

Question 14

Freezing/boiling point point analysis of RP:

Answer 14

• b.p exactly 100degC = pure water
• more impurities = higher b.p
• Freezing point exacly 0degC = pure water
• more impurities = lower freezing point

Question 15

What are the stages of the life cycle assessment?

Answer 15

1. extracting and processing raw material
2. manufacturing and packaging
3. use and operating over the lifetime
4. disposal of the product
5. transport of the product throughout each stage

Question 16

What are possible consequences of extracting and processing raw material?

Answer 16

does it us a lot of land
does it need lots of energy
does it pollute
is it renewable

Question 17

What are possible consequences of manufacturing and packaging

Answer 17

does it use a lot of energy
does it use lots of water
does it produce waste

Question 18

What are possible consequences of use and operating over the lifetime

Answer 18

can it be reused
does it need electricity or fossil fuels

Question 19

What are possible consequences of disposal of the product

Answer 19

can it be recycled
does it take a long time to decompose
is it biodegradable

Question 20

What are possible consequences of transport of the product throughout each stage

Answer 20

heavy items cos more to move

Question 21

Paper pos and neg

Answer 21

n - forests, land required, amounts of water used, heavy, not water resistant
p - trees take in CO2, renewable, low likelihood of huge environmental effect

Question 22

plastic pos and neg

Answer 22

n - made from oil, can cause environmental effects if oil spills
p - lightweight, can be used a lot
can be waterproof, recycled and durable

Question 23

stages of recycling

Answer 23

1. collect and sort
2. shared into smaller pieces
3. melt
4. reform into new product

Question 24

high grade ores:

Answer 24

ore- a rock that contains enough metal to be worth extracting. high grade ores have a high proportion of metal in the rock - copper ore is heated with carbon until the metal becomes a liquid and is poured off. this smelting uses lots of heat energy. high grade copper ores are running out

Question 25

low grade ores:

Answer 25

- little metal in them, so heating is expensive - get copper by bioleaching and phytomining

Question 26

Purifying copper:

Answer 26

making pure copper from copper compounds

Question 27

Electrolysis:

Answer 27

the electrolyte contains copper ions and the positive electrode is impure copper which dissolves and impurities fall off. pure copper is deposited on the negative electrode

Question 28

bioleaching

Answer 28

Certain bacteria can break down low-grade ores to produce an acidic solution containing copper ions. The solution is called a leachate and the process is called bioleaching Bioleaching does not need high temperatures but it produces toxic substances, including sulfuric acid, which damage the environment.

Question 29

phytomining

Answer 29

1. plants are grown on a low-grade ore 2. the plants absorb metal ions through their roots and concentrate these ions in their cells 3. the plants are harvested and burnt 4. the ash left behind contains metal compounds