C14 - The Earth's Resources

Question 1

Give two examples of renewable resources.

Answer 1

• Timber
• Fresh water
• Food

Question 2

Suggest one way in which chemistry is improving sustainability.

Answer 2

• Chemists have developed catalysts that reduce the amount of energy required for certain industrial processes.

Question 3

Sate two methods that can be used to extract copper from low grade ores.

Answer 3

BIOLEACHING:
- Bacteria used to convert copper compounds in ore into soluble copper compounds
- Separating copper form ore in the process
- Leachate (solution produced) contains copper ions - can be extracted by electrolysis or a displacement reaction
PHYTOMINING:
- Growing plants in soil that contains copper
- Plants don’t use/get rid of copper so it builds up in the leaves
- Plants are harvested an burned
- Ash contains soluble copper compounds (electrolysis or displacement reaction)

Question 4

Other than recycling, how can glass bottles be used in a sustainable way?

Answer 4

• Glass bottles can be reused without reshaping

- Glass is crushed and melted before being shaped and reused for bottles/ jars or insulating glass wool for homes

Question 5

What do Life Cycle Assessments (LCA) do and what are the four stages?

Answer 5

Looks at every stage of a products life to assess the impact it would have on the environment
- Getting the raw materials; manufacturing and packaging; using the product; product disposal)

Question 6

What is potable water and how is it made?

Answer 6

• Water that has been treated of naturally safe for humans to drink
  => Filtration: wire mesh - gravel and sand beds to filter out solid parts
  => Sterilisation: Kill harmful bacteria or microbes - bubbling chlorine gas through it or using ozone or ultraviolet light

Question 7

Suggest a source of fresh water.

Answer 7

Rain water

Question 8

Describe how you could distill seawater in the lab.

Answer 8

(Desalination)
=> Use a pH meter to measure pH of seawater - use titration to neutralise it
=> Test for sodium chloride (flame test = yellow; dilute nitric acid + silver nitrate solution - white precipitate)
=> Distill the seawater using heat
=> Retest for sodium chloride and retest for pH 7

Question 9

What other method could you use for making seawater potable?

Answer 9

• A process that uses membranes (like reverse osmosis)
  => salty water passed through membrane that only lets water molecule through
  => Ions and larger molecule are trapped by membrane and separated from the water

Question 10

Name three different sources of waste water.

Answer 10

• Domestic uses (e.g. baths, toilet etc.)
• Agricultural systems (e.g. nutrient run-off and slurry from animal farms)
• Industrial processes (e.g. Haber process)

Question 11

Why is it important to treat waste water before releasing it into the environment?

Answer 11

• Would pollute lakes, rivers etc. and pose health risks

- Remove organic matter and harmful microbes

Question 12

What type of waste water could contain harmful chemicals?

Answer 12

Industrial waste water

Question 13

What two products can be obtained by the anaerobic digestion of sewage sludge?

Answer 13

• Methane gas

- Digested waste (used as fertiliser)

Question 14

Describe the process of treating waste water.

Answer 14

1. Screening: removes large objects and grit
2. Sedimentation: heavier solids sink to bottom (sludge); light effluent floats on top
   3a. Aerobic Digestion: air pumped through tanks; encourages bacteria to break down organic matter
   4a. Released back into the Environment
   3b. Sludge removed and broken down by bacteria anaerobically
   4b. Releases methane gas an waste that is used as fertiliser
   (5. ) Waste water containing toxic chemicals has to have chemicals added (e.g. to precipitate metals), UV radiation or use membranes.