C14: The Earth's resources

Question 1

What do humans use resources for?

Answer 1

To provide warmth, shelter, transport and food.

Question 2

How are resources that we need produced in many cases?

Answer 2

Agriculture - helps us use the Earth’s resources more efficiently. e.g. grow wood for timber or biofuels.

Question 3

What is an example of chemistry replacing natural materials for synthetics ones?

Answer 3

Rubber - natural rubber comes from tree sap, but synthetic rubber is produced from crude oil. 2/3 of the world’s rubber is synthetic.

Question 4

What does finite mean?

Answer 4

Natural resources which cannot be replaced as quickly as they’re being used up.

Question 5

What are some examples of finite resources?

Answer 5

e.g. fossil fuels (humans use millions of kgs of fossil fuels everyday, which is much quicker than the rate at which fossil fuels form, meaning they will eventually run out.)
Metals - huge amounts extracted from the crust, continual usage means they will run out.

Question 6

What does renewable mean?

Answer 6

Resources that we can replace as quickly as they are used - will never run out.

Question 7

What are some examples of renewable resources?

Answer 7

Wood

Question 8

What is sustainability?

Answer 8

The ability for humans to meet their needs without preventing future generations from meeting theirs.

Question 9

How does chemistry allow us to become more sustainable?

Answer 9

Artificial fertilisers allows us to grow more food with the land available.
Helps provide water that is safe to drink (potable).
Processes like phytomining and bioleaching help extract metals more efficiently.

Question 10

What traits must drinking water have in order to be safe?

Answer 10

Low levels of dissolved salts e.g. sodium chloride.
Low levels of microbes.

Question 11

What is potable water?

Answer 11

Water that is safe to drink.

Question 12

Why is potable water not the same as pure water?

Answer 12

Pure water contains no dissolved substances at all (only consists of h2o molecules) whereas potable water can contain small amounts and still be drinkable.

Question 13

What is the main source of potable water in the UK?

Answer 13

Rainwater - low levels of dissolved substances.
Collects in the ground in aquifers, as well as in lakes, rivers and reservoirs. - sources of fresh water.

Question 14

How is potable water produced from rainwater?

Answer 14

Choose a good source of fresh water.
Pass the water through filter beds to remove materials such as leaves or suspended particles (large particles). Water is sterilised to kill microbes using chlorine, UV or ozone. No need for distillation due to the already low amount of dissolved minerals (smaller particles)

Question 15

How can potable water be produced from sea water (where countries don’t have access to fresh water)?

Answer 15

Sea water has high levels of dissolved minerals (potable water is produced through desalinisation). One way of carrying out desalination is using distillation. Another is to pass the water through partially permeable membranes (reverse osmosis).
These reduce the levels of dissolved substances.

Question 16

Compare distillation to reverse osmosis

Answer 16

Both methods require large amounts of energy - expensive

Question 17

What is water used for?

Answer 17

Small percentage for drinking.
Large amount for personal hygiene (baths and showers).
Flushing toilets and washing clothes.
Agriculture.

Question 18

Why does waste water need to be treated before being released into the environment?

Answer 18

Contains a large amount of dissolved substances (e.g. urine and faeces).
Large number of harmful microorganisms.
- must be carefully treated.

Question 19

Describe the process of treating waste water

Answer 19

1. Sewage is screened by passing through a mesh (removes solids and pieces of grit.
2. Sewage settles in large sedimentation tanks, producing a liquid effluent and a semi-solid sludge (sinks). Sludge is taken away and digested by anaerobic bacteria (in the absence of oxygen, these bacteria produce biogas, which can be burned for electricity.
   Digested sludge can be used as fertilisers for farming.
3. Liquid effluent contains large amounts of organic molecules and harmful microorganisms, which need to be reduced before water is returned to the environment. Air is bubbled through the liquid effluent (allows aerobic bacteria to multiply), in the presence of oxygen, the aerobic bacteria digest organic molecules and harmful microorganisms.
4. Liquid effluent is safely discharged into nearby rivers or the sea.

Question 20

How is water from industrial waste treated?

Answer 20

Harmful chemicals first need to be removed. After, water can sagely enter general sewage treatment.
Sometimes treated sewage water is used directly to produce potable water

Question 21

What are 3 sources of water?

Answer 21

Groundwater
Saltwater
Wastewater

Question 22

What is the easiest way to produce potable water?

Answer 22

Using groundwater from aquifers (safe to drink once treated with chlorine).
* aquifers can sometimes be polluted e.g. with fertilisers from farms. So water needs to be tested carefully.

Question 23

What are the negatives of making potable water directly from sewage?

Answer 23

Takes many purification steps - so only done in places where water is scarce

Question 24

What are the negatives of making potable water from seawater?

Answer 24

Needs to be desalinated (lots of energy and money)

Question 25

Why is there a demand for copper?

Answer 25

Used in electronic equipment (e.g. phones)

Question 26

When is it economical to extract a metal?

Answer 26

When its ore contains enough metal.
Less economical to extract a metal from a low grade ore because it contains a small amount of the metal.

Question 27

Why are we going to have to extract copper from low-grade ores?

Answer 27

Copper is scarce.

Question 28

What is a low-grade ore?

Answer 28

An ore which contains a very small amount of a metal.

Question 29

Describe the process of phytomining

Answer 29

• Plants are grown on land containing the metal compound that we want. Plants absorb the metal compound and concentrate it in their tissue.
  Plants are harvested and burned, and the ash contains a relatively high concentration of the metal compound.

Question 30

Describe the process of bioleaching

Answer 30

Uses bacteria
Bacteria are mixed with low-grade ore. They carry out chemical reactions and produce a solution called a leachate, which contains the metal compound that we want

Question 31

What do you need to do after the processes of bioleaching and phytomining?

Answer 31

Extract the metal from the metal compound produced.
- in the case of copper, we can displace copper using iron because scrap iron is cheap and more reactive than copper. Copper can also be extracted using electrolysis.

Question 32

What are some points about the processes of phytomining and bioleaching?

Answer 32

Allow us to economically extract metals from low-grade ores (important as Earth’s metal ores are limited).
Do not involve digging, transporting or disposing of large amounts of rock (unlike traditional mining)

Question 33

What is a life cycle assessment?

Answer 33

Attempts to put a number on the environmental impact of a product.

Question 34

What are the 4 main stages of lca?

Answer 34

Environmental impact of extracting and processing raw materials.
Packaging, manufacturing and transportation.
Impact of product during its lifetime.
Disposal of product at the end of its useful life

Question 35

Give some examples for stage 1 of the lca

Answer 35

Plastics - come from crude oil, which is extracted from the ground and transported to oil refineries. Hydrocarbons are separated and cracked. - processes take a large amount of energy, which is generated by fossil fuels which leads to climate change.
Metals - takes huge amount of energy. Ore is dug out of the mine and transported for processing. Metal is extracted from the ore, producing waste products

Question 36

Give an example for the environmental impact of a product at the end of its useful life

Answer 36

Many products have harmful chemicals which need to be disposed of carefully, which can take lots of energy.

Question 37

Compare the lca for plastic and shopping bags

Answer 37

Plastic - produced from crude oil (non-renewable, can harm habitats if there is an oil spill, chemically processed (lots of energy + waste))
- Strok, can be reused
- Transported to landfills - lighter
- Plastic is non-biodegradable, not broken down by microorganisms - remain in environment for a long time, so major form of litter and fill up landfills

Paper - made from wood from trees (renewable, destructive to forests, chemically processed, requires huge amounts of water)
- Weak, tear easily.
- Transported to landfills - heavier so take more energy
- Breaks down quickly

Question 38

What are some of the issues of lca?

Answer 38

Can measure use of water and energy, can also measure the production of some waste products.
Cannot always be certain of how damaging these are to the environment.
In some cases, we have to make estimates or value judgements which are not always accurate.
LCA can be biased (to support claims by advertisers)

Question 39

How are raw materials often obtained?

Answer 39

Through quarrying or mining- harmful to environment.
Takes lots of energy to convert raw materials into useful products.

Question 40

What are the negatives of quarrying and mining?

Answer 40

Quarrying - large amounts of dust and destroys habitats.
Mining - Release harmful chemicals into environment.

Question 41

Why is recycling good?

Answer 41

Saves limited resources and energy.
Reduces the amount of waste that we produce and has a less harmful effect on environment.

Question 42

How are metals recycled?

Answer 42

They are melted, then recast into different products

Question 43

What are the problems with recycling metals?

Answer 43

They usually need to be separated before being recycled (depends on the properties of final product)