C14 Flashcards
What is water distillation?
A seperation technique which involves a solution (salt water) being heated so that the solvent evaporates before being cooled to form a pure liquid (water).
What is desalination?
The process by which salt is removed from seawater in order to make drinking water
What are the 2 main methods of desalination?
Reverse osmosis and distillation
What is another word for distillation?
Thermal desalination
Why is desalination most commonly used in the Middle East?
- many of the countries are quite wealthy
- rainfall is low
- many of the countries have coastlines
What is reverse osmosis?
Reverse Osmosis is a method that is used to remove a large quantity of contaminants from water by pushing the water under pressure through a semi-permeable membrane.
Advantages of thermal desalination
- improves water quality
- kills harmful microbes in the water
- removes all impurities
Disadvantages of distillation
- heating uses a lot of energy
- energy may come from non-renewable sources
- expensive
Advantages of reverse osmosis
- no heating involved
- less energy required
Disadvantages of reverse osmosis
- need to pressurise water
- corrosion of pumps due to salty water
What are the 4 steps involved in treating waste water?
Screening, Primary Treatment, Secondary Treatment, Final Treatment
What is screening?
The waste water is passed through a metal grid which removes large objects such as branches
What is primary treatment?
Solids are allowed to settle out from the mixture, where large paddles push it to the centre to be piped off for further treatment
What happens during primary treatment?
Solids are allowed to settle out from the mixture, where large paddles push it to the centre to be piped off for further treatment
What happens during secondary treatment?
Bacteria are released in the liquid where they aerobically break down harmful micro-organisms and any other organic material. Air is bubbled through the liquid.
What happens during final treatment?
The bacteria are allowed to settle and are recycled or disposed with the solids
In waste water treatment, what happens to the solids (sludge)?
It is anaerobically digested by bacteria and then used as fertiliser/fuel or sent to landfill
What are the 2 main methods used to obtain copper from its ore?
- Smelting
- Sulfuric acid used to produce coper sulfate before extracting copper metal
What process is used to purify the impure copper extracted by smelting?
Electrolysis
How can copper be extracted from copper sulfate solution?
By adding iron which will displace copper from the solution
What is malachite?
A type of copper ore
What method is used 80% of the time to extract copper from malachite?
Smelting
Why is smelting bad?
Requires a lot of energy and emits Co2 and So4
What is phytomining?
Where plants are grown on low-grade copper ore which absorb copper ions. They are burnt; and the ash is reacted with sulphuric acid to form a leachate of copper sulphate, from which copper is obtained by displacement or electrolysis
What is bioleaching?
Where bacteria feed on low grade copper ore and produce a solution of copper ions called the leachate. Copper can be obtained from this by displacement or electrolysis
Why can copper be ocassionally found native?
Copper is an unreactive metal – it reacts only slowly with the atmosphere.