C12 - The Earth's Resources

Question 1

What are resources used for?

Answer 1

• Warmth
• Shelter
• Food
  and
• Waste disposal

Question 2

What is agriculture?

Answer 2

Farming. It helps us to use the earth’s resources more sustainably.

Question 3

Define finite in terms of resources.

Answer 3

A resource that can’t be replenished as quickly as it’s being used.

Question 4

Define renewable in terms of resources.

Answer 4

A resource being replenished as quickly as they’re being used.

Question 5

What is potable water?

Answer 5

Water that’s safe to drink (can have a low level of dissolved substances and mineral ions.)

Question 6

What is pure water?

Answer 6

Water with no dissolved substances at all.

Question 7

Where do we (the UK) get most of our potable water?

Answer 7

Rain water.

Question 8

How do we make water potable? (the process.)

Answer 8

• Collect fresh water
• Pass the water through filter beds to remove large objects (e.g leaves and suspended particles)
• Then the water is sterilised with chlorine, ozone or ultraviolet light.

Question 9

What is desalination?

Answer 9

The process of reducing the levels of dissolved minerals down to an acceptable level in sea water (v/salty).

Question 10

What are the two methods of desalination?

Answer 10

Distillation and reverse osmosis. They both require very large amounts of energy which makes them very expensive.

Question 11

What is distillation?

Answer 11

A separation technique used to separate the liquid from the mixture and keep the liquid.

In this case, it separates the water from the salt.

Question 12

What are the steps of distillation?

Answer 12

• The salt solution is placed into a flask and heated until it boils
• The water turns into a gas but the salt stays behind in the flask
• The steam passes into the condenser, which is a tube surrounded by a layer of cold water, which cools the steam and turns it back into a liquid. The distillate is potable water.

Question 13

What is reverse osmosis?

Answer 13

The passing of water through many membranes to desalinate it.

Question 14

Describe the water practical (testing for pure water - RQ8).

Answer 14

We need to test the pH and test for any dissolved solids. Pure water has a PH of 7 and no dissolved solids.

• We first check the pH by placing a small amount of the water nto some universal indicator paper.
• It must turn green if the pH is 7. If it turns any other colour (red is acidic, blue/purple is alkaline) then it is not pure.

Next we check for dissolved solids:
- First we record the mass of an empty evaporating basin using a mass balance.
- Then we take a sample of water and put it in the evaporating basin, on top of a tripod and gauze with a bunsen burner under it.
- The bunsen burner evaporates all the water and what’s left is any crystallised solids which were previously dissolved.
- If we can see the crystals or not we must weigh the evaporating basin again after it cools. If the mass increases, the water wasn’t potable. If it doesn’t, it’s probably potable.

Question 15

What is the problem with the water practical (RQ8)?

Answer 15

It doesn’t count for dissolved gases.

Question 16

What do humans use water for?

Answer 16

Drinking, personal hygiene, flushing toilets, washing clothes and agriculture.

Question 17

What is waste water?

Answer 17

Water that has been contaminated (with organic molecules (from urine and faeces) and harmful microorganisms)) and must undergo treatment before being released into other bodies of water.

Question 18

How is waste water treated?

Answer 18

• Sewage is screened through a sheet of mesh removing solids and pieces of grit.
• Then the sewage can settle, separating the liquid effluent and a semi-solid sludge which sinks.
• The sludge is taken away and digested by anaerobic bacteria (which produce a biogas which can be burned for electricity) and then can be used as fertilisers for agriculture.
• The liquid effluent has air bubbled through it, allowing aerobic bacteria to multiply.
• The aerobic bacteria digest the organic molecules and harmful microorganisms.
• Then the liquid effluent is discharged into the sea.

Question 19

What are the 3 sources we can produce potable water from?

Answer 19

Ground/fresh water (like rain water), sea water and wastewater.

Question 20

Ground/fresh water can sometimes be polluted with what?

Answer 20

Fertilisers.

Question 21

What is a metal ore?

Answer 21

A naturally occurring rock that contains enough metal to make it economical to extract the metal.

Question 22

What is a high grade ore?

Answer 22

An ore with a lot of metal:rock.

Question 23

What is a low grade ore?

Answer 23

An ore with little metal:rock.

Question 24

What are the two process of extracting copper economically?

Answer 24

Phytomining and bioleaching.

Question 25

What is phytomining?

Answer 25

The process of growing plants containing the metal compoud needed. The plants absorb the metal compoud and concentrate it in their tissue.
Then the plants are harvested and burned -> the ash contians a relatively high concentration of the metal compound.

Question 26

What is bioleaching?

Answer 26

The mixing of bacteria with the low grade ore. The bacteria carry out chemical reactions and produce a solution called a leachate. This leachate contains the metal compoud we want.

Question 27

After we use bioleaching and phytomining, how do we extract the metal from the compound?

Answer 27

Displacement. For copper we use iron (usually scrap iron which is cheap). We can also use electrolysis.