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What do we use natural resources for?
Energy and fuels for warmth
Building materials
Food
Materials for clothing
Define a finite resource
Resource that can only be used once and is in limited supply
How can we produce fertiliser from nitrogen?
The Haber process
How have synthetic fertilisers helped us?
They've allowed intensive farming to become more widespread → we can produce enough food to support the population
Define potable water
Water which is safe to drink
How can potable water be produced through fresh water?
Passing the water through filter beds to remove insoluble particles
Sterilising the water to kill microbes
↳ chlorine, ozone, ultraviolet light
Name the process which produces potable water from sea water
Desalination
How can desalination be done?
Distillation
Reverse osmosis
Describe the process of distillation
Sea water is heated until it boils
The steam is pure water so it is then condensed to make potable water
What are the disadvantages of distillation?
Requires a lot of energy → boiling and condensing
Waste water is very salty → hard to dispose of sustainably
Describe the process of reverse osmosis
Water is put under high pressure and passed through a membrane
The membrane has tiny holes → allows water molecules through but prevents most ions and molecules from passing
What are the disadvantages of reverse osmosis?
Membranes are expensive
Produces a large volume of waste water → low efficiency
What pollutants are present in waste water?
Bacteria
High levels of nitrogen compounds
Harmful chemicals
Fertilisers or pesticides
What is the process of sewage treatment
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
What are the 4 stages of a life cycle assessment?
Extracting and processing the raw materials
Manufacturing the product and its packaging
Using the product during its lifetime
Disposing of the product at the end of its useful life
What can LCA be criticised?
It is an objective process → different opinions
↳ may be bias
Define corrosion
The destruction of materials by chemical reactions with substances in the environment
When does corrosion happen?
When a metal continues to oxidise → Becomes weaker over time
What is the general equation for rusting?
Iron/steel + oxygen + water → hydrated iron/steel oxide
How can we prevent rusting
Keep oxygen/water away from iron or steel
Storing the metal in an atmosphere of unreactive nitrogen or argon
Using a dessicant
How can corrosion be prevented?
By applying a coating
↳ greasing, painting, electroplating
Why is potable water not pure water?
It contains dissolved substances → i.e fluorine
How can metals be reused?
Glass bottles
↳ crushed or melted to make other glass products
How can metals be recycled?
Melting
Recasting
Reforming
into different products
Why does aluminium not react with water?
Its surface is protected by a natural layer of aluminium oxide → resists corrosion
How can sacrificial protection prevent corrosion?
A more reactive metal is used as a coating which will be corroded by oxygen and water in place of the less reactive metal
Give 1 example of sacrificial protection
Galvanisation → coating iron with zinc
What can bronze be used for?
Coins
Statues
Bells
What is brass used for?
Musical instruments
Door knobs
Locks
What is carat used to measure?
The proportion of gold in a alloy
What is high carbon steel used for?
Construction → strong
What is low carbon steel used for?
Car body panels → malleable
What is stainless steel used for?
Cutlery → dosen't rust
What do the properties of a polymer depend on?
Which monomers they're made from
What conditions the monomers were joined together
What are the properties of low density polyethene?
Flexible
Unreactive
What are the properties of high density polyethene?
Strong
Flexible
resists shattering
Ressists chemical attack
What are the differences between the structure in low density and high density polyethene?
Low density → molecules are arranged randomly
High density → molecules line up more closely
What are thermosoftening plastics?
Plastics which melt when heated
Why do thermosoftening plastics melt?
They don't have covalent bonds between neighbouring polymer molecules → molecules can move over eachother
What are thermosetting plastics?
Plastics which char and burn when heated
What are composite materials?
Material made from two or more different materials with contrasting properties
What are most composites made of?
Matrix → binds the reinforcement together
Reinforcement→ Fibres or fragments of other materials
What process is used to make ammonia?
The Haber process
Where does the nitrogen for the haber process come from?
The air
Where does the hydrogen required for the Haber process come from?
Natural gas
Which catalyst is used in the Haer process?
iron
Why are fertilisers used?
To provide mineral ions needed for healthy growth in plants
What do most fertilisers contain?
Formulations of :
Nitrogen
Phosphorus
Potassium
Why do fertilisers have to be soluble?
So they can be dissolved in water and be absorbed by the root hair cells
What is produced when phosphate rock reacts with nitric acid?
Calcium nitrate + phosphoric acid
What is produced when phosphate rock reacts with sulfuric acid?
A mixture of calcium sulfate and calcium phosphate
What is produced when phosphate rock reacts with phosphoric acid?
Calcium phosphate
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