chemistry topic 10 (most important p2) Flashcards
what do earths resources provide
warmth, shelter, food
what is Sustainable development
meeting the needs of
current generations without compromising the ability
of future generations to meet their own needs
what is potable water
water that is safe to drink
how is most potable water produced
- choose an appropriate source of fresh water
- such as rivers, streams, lakes,
- pass through filter beds
- removes undissolved solids
- sterilise
- using chlorine / ozone / UV light
- destroys harmful microbes
what is Desalination
removing slat from salty water
what are the two types of desalination
Desalination by distillation
Desalination by reverse osmosis
using a membrane
what is a problem with both types of desalination
requires a large amount of energy
what does Sewage and agricultural waste water require removal of
- organic matter
- harmful microbes
what does Industrial waste water require removal of
- organic matter
- harmful chemicals
how is sewage treated
Screening or filtering to remove large solids
sedimentation – causing dirt to clump together to produce sewage sludge and effluent
anaerobic digestion of solid sewage sludge
aerobic biological treatment of liquid effluent
what is the practical for water purification
1) Have 3 samples of water from different sources
2) Place [10ml] water from each sample in the conical flask.
3) Heat the water using the Bunsen burner until it boils.
4) Reduce the heat so that the water boils gently.
5) The distilled water will collect in the cooled test tube.
6) Collect 1 cm of distilled water
7) Measure its boiling point.
Alternatively:
Measure mass of Conical flask + water
Boil all water
Measure new mass
The greater the mass left behind, the more the dissolved substances in the water sample
describe how photo mining is done
Grow plants (on land containing copper ores)
Plants are burnt (to produce ash)
Ash dissolved in acid (to produce a solution of a copper compound)
Electrolysis of acid (containing a copper compound)
describe bioleaching
Bioleaching uses bacteria to produce leachate solutions that contain (dissolved) metal
compounds.
why are Life cycle assessments (LCA’s) carried out
to assess the environmental impact of products
what do life cycle assessments look at
- Extracting and processing raw materials
- Manufacturing and packaging
- Uses and operation during
its Lifetime - Disposal at the end of it’s useful life, including transport and distribution at each stage
what are ways of reducing the use of resources
Reduction, reusing and recycling of materials reduces the
use of limited resources
how can glass bottles be recycled
Glass bottles can be crushed and melted to make different glass products.
how can metals be recycled
Metals can be recycled by melting and recasting or reforming into
different products.
what is corrosion
Corrosion is the destruction of materials by chemical reactions with substances in
the environment.
what is rusting an example of
corrosion
what must be present for iron to rust
air and water
how can corrosion be prevented
Corrosion can be prevented by applying a barrier, such as grease, paint or electroplating.
what is galvanising
Galvanising: Some of these coatings are reactive and contain a more reactive
metals to provide sacrificial protection, e.g. zinc is used to galvanise iron.
how does zinc galvanise iron
Zinc is more reactive than the iron, so zinc oxide will be produced in preference to iron oxide, thus protecting the iron from corrosion.
how is aluminium protected from corrosion
Aluminium has an aluminium oxide coating. Oxygen and water are unable to penetrate this layer to react with the aluminium atoms below. this protects the metal from further
corrosion.
what is bronze an alloy of
copper and tin
what is brass an alloy of
copper and zinc
what is gold for jewellery an alloy of
silver, copper and zinc
what does 24 carats and 18 carats mean when refereeing to gold
24 carat = 100% gold;
18 carat = 75% gold
what is steel an alloy of
iron and carbon
give features of high carbon steel
High carbon steel is strong but brittle
give features of low carbon steel
Low carbon steel is softer and more malleable
what are features of stainless steel that contains chromium and nickel
Stainless steels containing chromium and nickel are hard
and resistant to corrosion.
give features of aluminium alloys
Aluminium alloys are
low density
what type of glass is most of the glass we use
Soda-lime glass
how is soda-lime glass made
Heat sand, sodium
carbonate and limestone
how is Borosilicate glass made
Heat sand and boron
trioxide
Melts at a higher
temperature than soda-
lime glass
how are clay ceramics made
Shape wet clay
Heat in a furnace
e.g. pottery and bricks
describe composites
Most composites are made of two materials, a matrix or binder
surrounding and binding together fibres or fragments of the other material, which is called reinforcement.
give examples of composites
fibreglass, concrete, wood
what is produced from ethane
Low density (LD) and high density (HD) poly(ethene) are produced from ethene.
what are the conditions for low density poly(ethene) to be made
Temperature - Moderate
pressure - high
what are the conditions for high density poly(ethene) to be made
temperature - low
pressure - Low + catalyst
why does HDPE have a higher melting point that LDPE
LDPE have side chains; HDPE
have no side chains and have
stronger intermolecular
attractions between the chains
so have a higher melting point
how can polymers be categorised
Polymers can be categorised according to their overall structure and properties.
give the features of Thermosoftening polymers
- No crosslinks
- Low melting points
- Melt when heated
- Can be shaped when hot
give features of Thermosetting polymers
- Have crosslinks
- High melting points
- Do not melt when heated
- Cannot reshape
what is a closed system
Closed system – reactants and products react in a closed container
what makes Dynamic equilibrium
rate of the forward reaction = rate of reverse reactions
what are the conditions for the haber process
- A temperature of 450oC
- A pressure of 200 atmospheres
- An iron catalyst
nitrogen + hydrogen ⇌ ammonia
where does the nitrogen and hydrogen come from for the haber process
Nitrogen from air
Hydrogen from methane
why is 200 atmospheres the idea pressure for the haber prosses
- high pressure gives a high rate of reaction and yield of ammonia
- 4 moles of gas become 2 (or fewer moles of gas in products)
- too high a pressure causes risk of explosion + is expensive
why is 450°C the idea temprature for the haber prosses
- high temperature increases the rate of reaction
- forward reaction is exothermic so high yield of ammonia requires low temperature
- too low a temperature causes the rate of reaction to be too slow
why are iron catalysts used in Haber prosses
- a catalyst speeds up the reaction
- an iron catalyst allows a lower temperature to be used (saving energy and
causing a higher yield) - iron catalyst increases the rate of reaction equally in both reactions
give examples of NPK fertilisers
Nitrogen, Phosphorous, Potassium
what is Ammonium nitrate
Ammonium nitrate is a salt used as a fertiliser, produced from the
reaction between ammonia and nitric acid.
NH3 + HNO3 →NH4NO3
describe the Preparation of ammonium sulfate from ammonia solution and dilute sulfuric acid.
- Add known volume of dilute sulfuric acid to an
evaporating basin. - Add known volume and concentration of
ammonia to the sulfuric acid. - Test with universal indicator paper to ensure neutral.
- Evaporate the solution slowly using Bunsen
burner to concentrate the solution. - Cool until crystals form; dry the sample.
how are Potassium chloride, potassium sulfate and phosphate rock obtained
mining
how is phosphate rock different to Potassium chloride and potassium sulfate
phosphate rock (calcium phosphate) cannot be used directly as a fertiliser as it is insoluble.
how is phosphate rock treated so that it can become a fertiliser
Phosphate rock is treated with acid to produce soluble salts
Phosphate rock treated with nitric acid produces what
Calcium nitrate
Phosphate rock treated with sulfuric acid
produces waht
Calcium Sulfate
(Single superphosphate (SSP))
Phosphate rock treated with phosphoric acid
produces what
Calcium Phosphate
(Triple superphosphate (TSP))
