AQA GCSE CHEMISTRY - USING RESOURCES

Name four things for which humans require resources

Food, water, shelter, energy

Describe what is meant by finite and renewable resources

Finite: will run out (e.g. fossil fuels), Renewable: can be replenished (e.g. solar energy, crops)

What are synthetic resources and why do we use them?

Man-made alternatives, used because natural ones may be limited or less efficient

What is potable water?

Water that is safe to drink

How is this distinct from pure water?

Pure water contains only H₂O, potable water may contain safe levels of dissolved substances

Give three examples of substances that would stop water being potable

Harmful microbes, toxic metals, high salt concentrations

List the three key steps in providing potable water in the UK

Filtration, sedimentation, sterilisation

List three examples of ways water can be sterilised

Chlorine, ozone, UV light

Why is water sterilised?

To kill harmful microbes and bacteria

What is desalination?

Removing salt from seawater

Give two methods of desalination

Distillation, reverse osmosis

Why are these methods rarely used if fresh water is available?

Expensive, high energy use

What additional steps are required for treating agricultural waste water?

Removal of organic matter, harmful chemicals like fertilisers and pesticides

What additional steps are required for treating industrial waste water?

Removal of harmful chemicals, neutralisation

Name the four steps in sewage treatment

Screening, sedimentation, biological treatment, sludge treatment

HT only: What is an ore?

A rock that contains enough metal to make extraction economically viable

HT only: Why are alternative methods of extracting copper necessary?

High-grade ores are running out

HT only: What is phytomining?

Using plants to absorb copper from soil, then burning the plants

HT only: What is bioleaching?

Using bacteria to break down ores and produce copper-rich solutions

HT only: How can the solutions from phytomining and bioleaching then be processed?

By displacement with scrap iron or electrolysis

What is a life cycle assessment?

Analysis of a product's environmental impact from production to disposal

What are the four stages of an LCA?

Raw material extraction, manufacturing, use, disposal

Why is it challenging to assign a numerical value to pollutants?

It's subjective and depends on assumptions

How can LCAs be misused?

To support biased or misleading claims

Name three ways we can reduce the use of limited resources

Recycle, reuse, reduce

Name five materials made from limited raw resources

Metals, plastics, glass, ceramics, paper

How can glass be recycled?

Crushed, melted, reshaped

How can metal be recycled?

Melted and remoulded

Name two things that influence the amount of separation and processing required for recycling

Purity of material, type of material

What is corrosion?

The destruction of materials (often metals) by chemical reactions with the environment

Give an example of corrosion, and the conditions needed

Rusting of iron, requires oxygen and water

Name five ways corrosion can be prevented

Painting, greasing/oiling, galvanising, electroplating, sacrificial protection

Explain why zinc can be used to protect iron, but copper cannot

Zinc is more reactive and provides sacrificial protection, copper is less reactive

Define an alloy

A mixture of a metal with other elements to improve its properties

What are bronze and brass alloys of?

Bronze: copper and tin, Brass: copper and zinc

What is gold alloyed with in jewellery?

Silver, copper, zinc

Explain the "carat" system used for reporting gold purity

24 carat is pure gold, 18 carat = 18/24 = 75% gold

Describe the properties of high carbon, low carbon and stainless steels

High carbon: hard and brittle, Low carbon: softer and malleable, Stainless: corrosion-resistant

Describe the advantage of aluminium alloys

Low density, strong, corrosion-resistant

Give a use of bronze, brass, aluminium alloys, high carbon steel, low carbon steel and stainless steel

Bronze: statues, Brass: instruments, Aluminium alloys: aircraft, High carbon steel: tools, Low carbon steel: car bodies, Stainless steel: cutlery

How is soda-lime glass made?

Heating sand, sodium carbonate and limestone

How is borosilicate glass made?

Heating sand and boron trioxide

What is the advantage of borosilicate glass?

Higher melting point than soda-lime glass

How are clay ceramics made?

Shaping wet clay and heating in a furnace

What factors influence the properties of polymers?

Type of monomer, polymerisation conditions

How are thermosoftening polymers different to thermosetting polymers?

Thermosoftening can be remelted and reshaped, thermosetting cannot

Why is this the case?

Thermosetting polymers have cross-links between chains, thermosoftening polymers do not

What is a composite?

Material made from two or more different materials with combined properties

What is the purpose of the Haber process?

To make ammonia for fertilisers

What is the symbol equation for the Haber process?

N₂ + 3H₂ ⇌ 2NH₃

What are the raw materials of the Haber process?

Nitrogen and hydrogen

Where do these raw materials come from?

Nitrogen: air, Hydrogen: natural gas or cracking hydrocarbons

What are the reaction conditions for the Haber process?

450°C, 200 atm, iron catalyst

Why are these conditions used?

Compromise between yield and rate of reaction

How is ammonia extracted from this process?

Cooled, condensed, and removed as liquid

What is an NPK fertiliser?

Fertiliser containing nitrogen, phosphorus and potassium compounds

How are salts containing N, P and K obtained?

Nitrogen: from ammonia, Phosphorus: from phosphate rock, Potassium: from potassium salts in the Earth