C10.1 Chemistry- Using the Earths resources and obtaining potable water

How humans use Earths resources

We use resources for warmth, shelter, food and transport

Produced through agriculture

Eg cotton produced from a plant

Humans plant trees for timber of fuel

Many power stations use biofuel

Agricultre helps us use earyhs resources more efficiently

Synthetic alternative of natural resources

Natural rubber comes from the sap of a tree

Synthetic rubber is produced using crude oil

Around 2/3 of rubber used is synthetic

What are some finite resources

Finite- cant be replaced as quickly as theyre being used

Eg fossil fuels millions of kg used daily

Fossil fuels will run out

Eg metals huge amounts extracted from the earths crust

They will run out

what are some renewable resources and how are we as humans sustainable?

eg wood is replaced as quickly as used and will never run out

Important human activities are sustainable

Artificial fertillisers help us grow more food with the land available

Drinking water

Essential for human life, humans cant drink any water they find

Drinking water needs low level of dissolved salts such as sodium chloride

Drinking water cannot have high levels of microbes such as bacteria

What is potable water?

Water that is safe to drink

Contains dissolved substances in small amounts

Potable water production

Rainwater provides most of our potable water

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

Rivers are a good example of fresh water

Sterilisation

Choose a source of fresh water and pass it through filter beds to remove leaves and suspended particles

Water is sterilised to kill microbes, chlorine is used to sterilise potable water in the UK

In other countries ozone or ultraviolet light is used

What if the only available water is sea water?

Fresh water can sometimes be scarce

Only available water is sea water

Sea water has very high levels of dissolved minerals

Potable water is produced by desalination

Desalination reduces the levels of dissolved minerals down to an acceptable level of potable water.

Ways of carrying out desalination

Distillation

Another way is to pass the water through membranes known as reverse osmosis

Distillation and reverse osmosis reduce the levels of dissolved minerals

Both processes require a lot of energy making them very expensive

Water uses

Personal hygiene, flushing toilets, agriculture

This waste water contains organic molecules eg from urine, faeces

Contains harmful microorganisms

The waste water must be carefully treated before released back into environment

How to treat waste water?

Sewage is screened by passing througb a mesh removing solids and grit

Sewage can settle in sedimentation tanks producing effluent and sludge which sinks

Sludge is taken away and digested by anaerobic bacteria

Effluent contains harmful microorganisms and organic molecules at the end

Aerobic bacteria digests the organic molecules and harmful microorganisms

Effluent can be safely discharged into nearby rivers or sea

Sewage treatment

Water is used by industry

Harmful chemicals need to be removed to treat this water

Water can then enter general sewage treatment

How can potable water be produced?

Easiest way is to use groundwater from aquifers

Once treated with chlorine it is safe to drink

Can be made from waste water such as sewage

Takes many purification steps so only done when water is scarce

Salt water needs to be desalinated to produce potable water