Using resources

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?

1. Passing the water through filter beds to remove insoluble particles

2. 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

1. screening and grit removal to remove large particles

2. sedimentation allows tiny particles to settle out from still water, which produces sewage sludge and effluent (the liquid which remains on top)

3. the sewage sludge is digested anaerobically by specific bacteria

4. the effluent is treated with aerobic bacteria to reduce the volume of solid waste

What are the 4 stages of a life cycle assessment?

1. Extracting and processing the raw materials

2. Manufacturing the product and its packaging

3. Using the product during its lifetime

4. 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