C14-Water And Resources Flashcards
How do humans use the resources of the world
Humans use the resources of the world to provide warmth, food, shelter and transport
How are these resources produced
- 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
What has chemistry changed about resources
- 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
What is a finite resource
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
What is another example of a finite resource
- 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
What are renewable resources
Renewable resources are resources we can replace as quickly as they are being used up
E.g wood
What is sustainability
Sustainability involves meeting the needs of our generation without preventing future generations meeting their needs
How can chemistry help to produce more resources
The invention of products such as artificial fertilisers allows us to grow more crops with the land avaliable
Why cant humans drink any water
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
What is potable water
Potable water is water that is safe to drink it contains dissolved substances in small amounts
What is pure water
Pure water in the chemical sense is water that contains no dissolved substances at all
Where does most potable water come from in the UK
-In the UK most of our potable water comes from rain water . Rainwater contains small amounts of dissolved substances
Where can rainwater be collected from
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
What are the steps used to make rainwater Potable water
- 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
What is desalination
- 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
What does desalination do to the sea water to produce potable water
-Desalination reduces the levels of dissolved minerals in sea water down to an acceptable level for potable water
What are two ways to perform desalination
- Desalination can be done use distillation
- This processes reduce the amount of dissovled minerals in sea water
What are the problems with these processes of desalination
These processes of desalination require lots of energy meaning they are expensive
What other ways is water used
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
What is this water classed as
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
Describe the process involved in treating waste water
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
What needs to happen to water that has been used in industry before it can go into general sewage treatment
-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
What can treated waste water be used for in some parts of the world
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
What happens during reverse osmosis
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
