Finite and renewable resources, how drinking water is produced and why potable is not the same as pure, desalination, sewage treatment, and extracting metals with plants and bacteria.
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1.What is a finite resource?
One that is being used up faster than it can be replaced, so supplies will eventually run out.
2.What is a renewable resource?
One that can be replaced at the same rate as it is used, so supplies do not run out.
3.Give an example of a finite resource.
Crude oil, natural gas, coal and metal ores.
4.What does sustainable development mean?
Meeting the needs of people today without stopping future generations meeting their own needs.
5.What does potable mean?
Water that is safe to drink.
6.Why is potable water not the same as pure water?
Potable water still contains dissolved substances. Pure water in the chemical sense contains nothing but H2O.
7.What two things must be true of potable water?
It must have low levels of dissolved salts, and low levels of microbes.
8.Where does most UK drinking water come from?
Rainwater collected in the ground, in lakes, and in rivers.
9.Describe how fresh water is treated to make it potable.
It is passed through filter beds to remove solids, then sterilised to kill microbes.
10.Name three ways water can be sterilised.
Chlorine, ozone, or ultraviolet light.
11.What is desalination?
Removing the salt from sea water to make it potable.
12.Name two methods of desalination.
Distillation, and reverse osmosis using membranes.
13.Why is desalination not used everywhere?
It requires very large amounts of energy, so it is expensive.
14.When is desalination used despite the cost?
In countries where there is not enough fresh water available.
15.Why must waste water be treated before release?
It contains organic matter and harmful microbes that would pollute rivers and spread disease.
16.What is the first stage of sewage treatment?
Screening and grit removal, which takes out large solids and grit.
17.What happens during sedimentation?
The sewage settles, producing sludge which sinks and effluent which stays on top.
18.How is the sludge treated?
By anaerobic digestion, which breaks it down and produces biogas that can be used as a fuel.
19.How is the effluent treated?
By aerobic biological treatment, where air is bubbled through so bacteria break down the organic matter.
20.Why is air bubbled through the effluent?
The bacteria that break down the organic matter respire aerobically and need oxygen.
21.Why is treating sea water harder than treating waste water?
Salt is dissolved throughout the water, so it cannot be filtered out and must be removed by energy intensive methods.
22.What is phytomining?
Growing plants on land containing low grade metal ore. The plants absorb metal compounds, are harvested and burned, and the metal is extracted from the ash.
23.What is bioleaching?
Using bacteria to produce leachate solutions containing metal compounds, from which the metal can be extracted.
24.How is the metal obtained from the leachate or ash?
By displacement using scrap iron, or by electrolysis.
25.Give an advantage of phytomining and bioleaching.
They allow metals to be extracted from low grade ores that would otherwise be uneconomic, and they avoid the damage caused by traditional mining.
26.Give a disadvantage of these biological methods.
They are slow processes compared with conventional mining.
27.In the required practical on water, what is analysed?
Samples of water are tested for dissolved solids, and then purified by distillation.
28.How do you find the mass of dissolved solids in a water sample?
Evaporate a known volume to dryness and weigh the solid residue that remains.
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