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Topic 10 Using Resources By Bethan Poole (10.1 Using the Earth's…
Topic 10 Using Resources
By Bethan Poole
10.1 Using the Earth's resources and obtaining potable water
10.1.1 Using the Earth's resources and sustainable development
We rely on human resources for warmth, shelter, food and transport
All resources come from the Earth's crust , oceans or atmosphere
Can be renewable or non-renewable(finite)
Finite resources must be used with great care
We must to take to ensure planet doesn't become too polluted
As population grown we cannot only rely on natural resources but now we must use agriculture to supplement or replace natural resources
Chemistry helps improve agricultural and industrial processes- helps new products be developed and contributes to sustainable development
Synthetic material examples
Rubber replaced by man-made polymers
Wood replaced by plastics i.e. laminate floors
10.1.2 Potable Water
Water is essential for life
Water naturally contains microorganisms and dissolved salts- these must be at low levels for it to be safe to drink
Fresh water contains low levels of dissolved salts
Water that is safe to drink is called potable
UK potable water produced by
1)
Fresh water from a suitable source
2)
Passed through a filter bed to remove solid particles
3)
Chlorine gas added to kill harmful microorganisms
4)
Fluoride added to reduce tooth decay
Ozone and ultraviolet can be used to sterilise water
To improve taste more dissolved substances can be removed- i.e. passing water through a filter containing carbon, silver and ion exchange resin
Seawater
can be desalinated
either done by distillation or reverse osmosis
Very expensive (require lots of energy)
Distillation- Water boiled to produce steam, steam condensed to produce pure liquid water
10.1.3 Waste Water Treatment
Large amounts of waste water produced by homes, agriculture and industry
Waste water must be treated before it can be safely released into environment
Organic matter, harmful microorganism and toxic chemicals have to be removed
Sewage water treatment
1)
Screening and grit removal
2)
Sedimentation to produce sewage sludge and effluent
3)
Anaerobic digestion of sewage sludge
4)
Aerobic biological treatment of effluent
10.1.4 Alternative methods of extracting metals
Copper
Useful metal
Good because
Good conductor of electricity and heat
Easily bent but hard enough to make pipes
Doesn't react with water- lasts for a long time
Can be extracted from ores by heating with carbon in a furnace-
smelting
Purified by electrolysis
Also obtained: from solutions of copper salts (electrolysis), Displacement using scrap iron
Electrolysis- positive copper ions move to cathode- forms pure copper
Extensive mining of copper means we are running out of copper rich ores- we have to extract from ores containing less copper
Can be extracted by
Low-grade ores
Contaminating land by biological methods
Phytomining
Method when plants absorb copper
As plants grow they absorb and store copper
Plants then burned and ash produced contains copper in high quantities
Bioleaching
Uses bioleaching to extract metals from low-grade ores
Solution containing bacteria mixed with a low-grade ore
Bacteria converts copper into a solution from which copper can be easily extracted
10.2 Life cycle assessment and recycling
10.2.1 Life cycle assesment
Carried out to assess the environmental impact of product over its lifetime
Provide a way of comparing several products
Scientists measure the impact of
Extracting and processing raw materials
Manufacturing and packaging
Use and operation during its lifetime
Disposal at end of useful life
Some aspects of the LCA easy to quantify i.e. Energy, water and raw materials
Some involve value judgements i.e. impact of pollutant on environment
10.2.2 Ways of reducing the use of resources
Materials like glass, metals and plastics are important to our standard of living
Must be used wisely and reused/ recycled when possible to...
Save money and energy
Make sure natural resources are not used up unnecessarily
Reduce amount of waste produced
Reduce damage to the environment caused by extraction
Metal, glass, building materials and plastics made from crude oil are produced from limited resources
Supplies of these raw materials and fossil fuels used to obtain them are finite
Some objects can be reused
Waste glass can be crushed, melted and reused
Some waste plastic can be recycled to make fleece materials
Metals can be recycled by melting them down and making new objects
10.3 Using materials
10.3.1 Corrosion and its prevention
Metals corrode when they react with oxygen and water in the evironment
Rusting often used when metals containing iron corrode
Iron + water + oxygen -> hydrated iron (III) oxide
Prevention
Painting , electroplating or greasing a metal object to stop oxygen and water from reaching surface
Damaged coating- metal will begin to corrode
Sacrificial protection
More reactive metal placed in contact with metal
I.e. Blocks of magnesium attached to iron- magnesium more reactive so reacts and loses electrons instead of iron
Galvanising
Object coated in layer of zinc- stops oxygen and water reaching metal- stops corrosion
If zinc surface scratched- then zinc provides sacrificial protection
Aluminium protected by thin aluminium oxide layer- acts as a barrier
10.3.2 Alloys as useful materials
Mixture of metals- most metals we use are alloys
Examples
- Bronze (copper and tin) and Brass (copper and zinc)
Gold
Alloy with silver, copper and zinc
Proportion of gold measured in carats- 24 carat= 100% pure gold
18 carat=75% gold
Steel
Alloys of iron contain specific amounts of carbon and other metals
High carbon steel is strong but brittle, low carbon steel is softer and more malleable
Stainless steels- contain chromium and nickel- hard and resistant to corrosion
Aluminium alloys are low density
10.3.3 Ceramics, polymers and composites
Glass
Soda-lime glass made by heating a mixture of sand, sodium carbonate and limestone- used as window glass
Borosilicate glass (pyrex)
Made by heating sand and boron trioxide together to a higher temp. than needed for soda-lime glass
Used to make chemical glassware, cooking equipment and car headlights
Glass is a non-crystalline solid- many different types
Ceramics
Pottery and bricks are clay ceramics- made by shaping wet clay and then heating in a furnace
Furnace removes the water so can retain shape- harder and stronger
Composites
Produces a material that has its own improved qualities
e.g. Concrete, fibreglass and carbon fibre
Fibres or fragments of one material surrounded by a material called a binder or matrix
Consist of 2 materials with different properties
Polymers
Thermosoftening
Weak inter molecular forces
Low melting points
Thermosetting
Strong inter molecular forces (cross links) between molecules
High melting points and are rigid
Low density polyethene
Soft and flexible
Used in bags and clingfilm
Monomer- ethene
Reaction conditions- 200C, 2000atm pressure, oxygen catalyst
High density polyethene
Hard + strong
Used in buckets and pipes
Monomer- ethene
Reaction conditions- 60C, 2atm pressure, ziegla-natta catalyst
10.4 The Haber process and the use of NPK fertilisers
10.4.1 The Haber Process
Reversible reactions may not go into completion but can be used efficiently in continuous processes like the Haber Process
Used to manufacture ammonia- produces nitrogen- based fertilisers
Raw materials needed
Purified nitrogen- from fractional distillation or liquid air
Hydrogen from natural gas or steam
Nitrogen and hydrogen added to iron catalyst at 450C (moderate) and 200atm pressure (high)
Some hydrogen and ammonia react to produce ammonia
Reversible reaction- some ammonia breaks down into hydrogen and nitrogen
Ammonia is cooled and liquefies so can be removed from mixture
Unreacted nitrogen and hydrogen is recycled
Nitrogen + Hydrogen
Ammonia
N2 + 3H2
2NH3
Choosing Conditions
Reaction is exothermic
High temp. = fast rate of reaction but low yield
Low temp.= high yield but slow rate of reaction
Moderate temp. used and high pressure to encourage high yield
Iron catalyst to increase rate of reaciton
10.4.2 Production and uses of NPK fertilisers
Fertilisers used to replace essential elements in soil that are used up as they grow
Chemicals absorbed through plants roots - fertilisers must be soluble in water
Plants need nitrogen (N), phosphorus (P) and potassium (K) to grow well
NPK fertilisers are formulations of various salts- mixed together to give appropriate % of each element
NPK rating of fertiliser consists of 3 numbers
e.g. 16-4-10
1st number= % of nitrogen
2nd number= amount of phosphorus
3rd number= amount of potassium
Ammonia is an alkaline gas that dissolves in water- mainly used in fertilisers to increase nitrogen content in soil
Ammonia
Can be oxidised to produce nitric acid
Can neutralise nitric acid to produce ammonium nitrate-
ammonia+ nitric acid -> Ammonia nitrate
NH3 (aq)+ HNO3 (aq) -> NH4NO3 (aq)
Ammonia nitrate - fertiliser rich in nitrogen- important as it increases the yield of crops
Potassium chloride and potassium sulfate are soluble so can be used directly as fertilisers
Phosphate rock
Contains high levels of phosphorus compounds- these are insoluble so can't be directly used
Can be processed to make useful new products
Treated with nitric acid- produces phosphoric acid and calcium nitrate. Phosphoric acid neutralised with ammonia to produce ammonia phosphate
Reacted with sulfuric acid to make single superphosphate- mix of calcium phosphate and calcium sulfate (sulfur needed for plants to grow well)
Reacted with phosphoric acid to make triple superphosphate (calcium phosphate)
