C14-Water And Resources

Question 1

How do humans use the resources of the world

Answer 1

Humans use the resources of the world to provide warmth, food, shelter and transport

Question 2

How are these resources produced

Answer 2

• Resources are produced using agriculture. A good example of this is cotton which is picked from plants
• Modern agriculture allows us to grow enough cotton to meet the needs of the world today

Question 3

What has chemistry changed about resources

Answer 3

• Chemistry has replaced natural resources a synthetic alternative e.g rubber
• Natural rubber comes from the sap of the tree whereas synthetic rubber is produced using crude oil
• Now around 2/3 of the rubber used in the world is synthetic rubber

Question 4

What is a finite resource

Answer 4

A finite resource is a resource that cannot be replaced as quickly as it is being used e.g fossil fuels

-Humans use millions of kgs of fossil fuels but the rate fossil fuels are being produced is much slower than this

Question 5

What is another example of a finite resource

Answer 5

• Metal is another finite resource
• Huge amounts of metal ore are being extracted from the ground. If we continue using and extracting metals at this rate they will run out

Question 6

What are renewable resources

Answer 6

Renewable resources are resources we can replace as quickly as they are being used up

E.g wood

Question 7

What is sustainability

Answer 7

Sustainability involves meeting the needs of our generation without preventing future generations meeting their needs

Question 8

How can chemistry help to produce more resources

Answer 8

The invention of products such as artificial fertilisers allows us to grow more crops with the land avaliable

Question 9

Why cant humans drink any water

Answer 9

Humans cant drink any water they find as drinking water has to have sufficiently low levels of salts and cannot have high levels of microbes e.g bacteria

Question 10

What is potable water

Answer 10

Potable water is water that is safe to drink it contains dissolved substances in small amounts

Question 11

What is pure water

Answer 11

Pure water in the chemical sense is water that contains no dissolved substances at all

Question 12

Where does most potable water come from in the UK

Answer 12

-In the UK most of our potable water comes from rain water . Rainwater contains small amounts of dissolved substances

Question 13

Where can rainwater be collected from

Answer 13

Rainwater collects in the ground in aquifers and in lakes ,rivers and resevoirs

Note:in some places aquifers can be polluted with chemicals from fertilisers so the water in aquifers needs to be tested carefully

Question 14

What are the steps used to make rainwater Potable water

Answer 14

• To produce potable water you first choose an appropraite source of water e.g lake and collect water
• You then pass the water through filter beds. This removes any materials e.g leaves and suspended particles
• Finally the water is sterilised to kill any microbes e.g bacteria . In the Uk chlorine is used to do this but in other parts of the world it can be done using ozone or UV light

Question 15

What is desalination

Answer 15

• Desalination is a process where sea water is used to produce potable water
• It is used in countries with a scarce supply of fresh water

Question 16

What does desalination do to the sea water to produce potable water

Answer 16

-Desalination reduces the levels of dissolved minerals in sea water down to an acceptable level for potable water

Question 17

What are two ways to perform desalination

Answer 17

• Desalination can be done use distillation

- This processes reduce the amount of dissovled minerals in sea water

Question 18

What are the problems with these processes of desalination

Answer 18

These processes of desalination require lots of energy meaning they are expensive

Question 19

What other ways is water used

Answer 19

Large amounts of water is used for hygiene e.g baths and showers ,

• large amounts of water is used for flsuhing toilets and washing clothes.
• Large amounts of water is also used in industry

Question 20

What is this water classed as

Answer 20

This water (for flushing toilets, industry , hygeine )is classed as waste water and it usually contains harmful microorganisms and organic matter e.g urine feaces

-This water must be treated carefully before it is released back into the environment

Question 21

Describe the process involved in treating waste water

Answer 21

1) In the first stage, sewage is screened by passing it through a mesh , this removed pieces of grit and solids
2) The sewage is then allowed to settle in large sedimentation tanks
3) This settling produces a semi sold sludge which sinks to the bottom of the tank and a liquid effluent
4) The sludge is taken away and digested by anearobic bacteria . In the abscence of oxygen these bacteria produce biogas which can be burned for electricity . At the end the digested sludge can be used as fertiliser for farming
5) The liquid effluent which settled at the top still contains harmful microogranisms and organic matter which need to be reduced before the liquid can be returned to the environment
5) to remove these things air is bubbled through the effluent which allows aerobic bacteria to multiply
6) In the presence of the oxygen the aerobic bacteria digest the harmful microorganisms and the organic molecules
7) After this the liquid effluent can safely be discharged into nearby rivers or the sea

Question 22

What needs to happen to water that has been used in industry before it can go into general sewage treatment

Answer 22

-For water that has been used in industry any harmful chemicals must first be removed from the water before it can enter general sewage treatment

Question 23

What can treated waste water be used for in some parts of the world

Answer 23

In some parts of the world treated waste water is used to directly produce potable water but this takes a lot of purifaction so is only used in places where water supply is scarce

Question 24

What happens during reverse osmosis

Answer 24

During reverse osmosis presssurised sea water is passed through a semi permeable membrane to seperate the water from the salts dissolved in it . The membranes remove the dissolved substances from the water

• Energy is still used to pressurised the water
• A problem is corrosion of pumps by salty water

It is used in hot,dry wealthy countries