Anku Flashcards
Define ‘finite’ and give examples of finite resources.
Finite - the rate of use is faster than the rate of production e.g. metal ores, fossil fuels
Define ‘renewable’ and give an example of renewable resources.
Renewable - The rate of production is faster than the rate of use e.g. timber (biomass)
What do humans use the Earth’s resouces to provide (4 things)?
- warmth - shelter - food - transport
In the past, natural resources were sufficient enough to provide humans with food, timber, clothing and fuels. But as the population has grown, what have we used to supplement (or even replace) natural resources?
Agriculture (and synthetic products)
Give an example of how agriculture has supplemented natural resources.
Fertiliser derived from manure is used to fertilise crops.
Define sustainable development.
Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs. (Chemistry plays an important role in providing new products through sustainable development)
Define pure water.
Water that contains no other additives (only H20)
Define potable water.
Water that is safe to drink (meaning low levels of dissolved salts and microbes and a safe pH (between 6.5 and 8.5))
Describe the fresh water treatment process (and where it is used).
In the UK, most potable water is produced from fresh water (rain water in lakes and rivers and then resevoirs). 1) Grated bars - water is passed through grated bars to remove twigs and leaves 2) Settlement tank - sand and soil sinks to the bottom 3) Chemicals - ionic salts are added to make the dirt clump together and sink 4) Filter - water passes through a filter made of fine sand (the water is now clear) 5) Sterelisation - water may contain deadly microbes so it is sterelised with UV light, ozone (O3) or chlorine (Cl2) 6) pH - the pH is checked and changed if needed (must be between 6.5 and 8.5) (Sometimes fluroine is added to drinking water to reduce tooth decay) Then water is stored until needed.
What are the two ways salt water can be purified (desalination) and where are they most likely to be used?
1) Distillation 2) Reverse Osmosis These are most likely to be used by countries with a small fresh water supply but large supply of fossil fuels to provide the energy for desalination. e.g countries in the middle east
Describe distillation including its pros and cons (compared to reverse osmosis)?
- A sample of water is heated and evaporated. - It passes through the condensing tube and condenses - The pure water is then collected - This is a batch process Pros (compared to reverse osmosis): - Equipment doesn’t need replacing as often - Doesn’t require high pressure Cons: - requires heating (burning fosil fuels) - batch process (needs to stop and start)
Describe reverse osmosis including its 2 pros and 2 cons (compared to distillation) ?
- A partially-permeable membrane is used to separate fresh water and salt water - Under high pressure, water in the salt water moves to the fresh water across the partially permeable mebrane Pros: - doesn’t require heating (reduces burning of fossil fuels) - continuous process (doen’t require stopping) Cons: - Equipment (pumps and membrane) often need replacing as they corrode - Requires high pressure (lots of energy)
What is the main disadvantage of desalination (both processes) in comparison to fresh water treatment?
Both processes require large amounts of energy making them very expensive. This is why desalination is only done when fresh water supplies are limited.
What does ‘Heat to Constant mass’ mean?
It means removing, weighing once cool and replacing sample (of water) to the heat until the mass does not decrease any further
Describe RP 8 (including results and mistakes) - analysis and purification of water samples
Make sure there is nothing in the watch glass to avoid an anomalous result.1) Weigh the mass of the empty watch glass. 2) Fill with water sample 3) Weigh the mass of the watch glass with water. 4) Over a water bath (to control temperature), heat to constant mass 5) Weigh the watch glass at the end of heating to constant mass to find the mass of solid (Step 5 - Step 1) 6) Calculate the solid percentage Repeat with other samples 7) Separately, test the pH using universal indicator and use the pH colour chart to identify the pH Results: If a sample has a large mass of solid, the water contains lots of ions Reasons for anomalous results: The watch glass may have had water on it at the start during ‘empty’ weighing (so the mass of solid is negative)
