C14 Flashcards
What is pure water?
Water that contains only water molecules
What is potable water?
Water safe to drink. It is not pure as it contains dissolved substances
How do you treat fresh water?
- filter out debris, let large dirt settle to the bottom
- sterilise with chlorine, ozone or UV light
How do you treat salt water?
- filter out debris
- desalinate (remove salt) by either distillation (high temp) or reverse osmosis (high pressure)
what is the process of treating wastewater?
- screening and grit removal to remove large particles
- sedimentation allows tiny particles to settle out from still water, which produces sewage sludge and effluent (the liquid which remains on top)
- the sewage sludge is digested anaerobically by specific bacteria
- the effluent is treated with aerobic bacteria to reduce the volume of solid waste
- Then sterilised and clean water goes into the river
compare the treatments of fresh and salt water
fresh: cheaper, less energy used, quicker to process
salt: expensive as high temp and pressure use a lot of energy, salt corrodes (wears down) pumps
describe the process of distillation (in desalination)
Sea water is heated until it boils. The salt remains in the liquid, and the steam is pure water. The steam is cooled and condensed to make potable water. (done by distillation)
describe the process of reverse osmosis (in desalination)
Water is put under high pressure and passed through a
membrane which has tiny pores (holes) in it. The pores allow water molecules through, but prevent most ions and molecules from passing through
What are the problems of distillation?
requires a lot of energy to boil the water, and also to cool the steam down to condense it. The waste water is very salty and can be difficult to dispose of in a
sustainable way which does not harm marine ecosystems
What are the problems of reverse osmosis?
requires expensive membranes and also produces a large volume of waste water, so its
efficiency is often quite low.
what’s sustainable development?
- meets the needs of current generations without compromising ability of future generations to meet their needs
What are synthetic products, and what are some examples?
- man-made materials which replace or supplement natural resources
instead of wool, polymer (polyester)
instead of rubber, polymer
If asked to “devise a fair test on a 100cm3 sample of water”, you must:
- divide sample into smaller volumes to see if results are reproducible
- always record the mass of any evaporating dishes before and after heating to calculate the difference
- always use clean, dry equipment
pH analysis of RP:
- low pH = acid rain or distilled water
- high pH = water from carbonate rocks/dissolved minerals.
- Pure water = pH7
Freezing/boiling point point analysis of RP:
- b.p exactly 100degC = pure water
- more impurities = higher b.p
- Freezing point exacly 0degC = pure water
- more impurities = lower freezing point
What are the stages of the life cycle assessment?
- extracting and processing raw material
- manufacturing and packaging
- use and operating over the lifetime
- disposal of the product
- transport of the product throughout each stage
What are possible consequences of extracting and processing raw material?
does it us a lot of land
does it need lots of energy
does it pollute
is it renewable
What are possible consequences of manufacturing and packaging
does it use a lot of energy
does it use lots of water
does it produce waste
What are possible consequences of use and operating over the lifetime
can it be reused
does it need electricity or fossil fuels
What are possible consequences of disposal of the product
can it be recycled
does it take a long time to decompose
is it biodegradable
What are possible consequences of transport of the product throughout each stage
heavy items cos more to move
Paper pos and neg
n - forests, land required, amounts of water used, heavy, not water resistant
p - trees take in CO2, renewable, low likelihood of huge environmental effect
plastic pos and neg
n - made from oil, can cause environmental effects if oil spills
p - lightweight, can be used a lot
can be waterproof, recycled and durable
stages of recycling
- collect and sort
- shared into smaller pieces
- melt
- reform into new product
high grade ores:
ore- a rock that contains enough metal to be worth extracting. high grade ores have a high proportion of metal in the rock
- copper ore is heated with carbon until the metal becomes a liquid and is poured off. this smelting uses lots of heat energy. high grade copper ores are running out
low grade ores:
- little metal in them, so heating is expensive
- get copper by bioleaching and phytomining
Purifying copper:
making pure copper from copper compounds
Electrolysis:
the electrolyte contains copper ions and the positive electrode is impure copper which dissolves and impurities fall off. pure copper is deposited on the negative electrode
bioleaching
Certain bacteria can break down low-grade ores to produce an acidic solution containing copper ions. The solution is called a leachate and the process is called
bioleaching
Bioleaching does not need high temperatures but it produces
toxic substances, including sulfuric acid, which damage the environment.
phytomining
- plants are grown on a low-grade ore
- the plants absorb metal ions through their roots and concentrate these ions in their cells
- the plants are harvested and burnt
- the ash left behind contains metal compounds
