Using Resources

What are natural resources?

Resources obtained from the Earth, oceans or atmosphere that humans use.

What do humans use Earth's resources to provide?

Warmth, shelter, food + transport.

Give examples of natural resources supplemented or replaced by agricultural/synthetic products.

Timber can be supplemented by cultivated forests - natural fibres can be supplemented/replaced by synthetic fibres.

What is a finite resource?

Resource that is used faster than it is naturally replaced and will eventually run out.

What is a renewable resource?

Resource that is naturally replenished at approximately the rate it is used.

What is sustainable development?

Development that meets the needs of current generations without compromising the ability of future generations to meet their needs.

How can chemistry contribute to sustainable development?

Reduce use of limited resources, energy use, waste + environmental impacts.

What is potable water?

Water that is safe to drink.

Is potable water chemically pure water?

No - it contains low levels of dissolved substances.

What properties should potable water have?

Sufficiently low levels of dissolved salts + microbes.

How is fresh water made potable in the UK?

Choose suitable fresh-water source - pass through filter beds - sterilise.

What does filtration do during water treatment?

Removes insoluble solid particles.

Why is potable water sterilised?

To kill harmful microorganisms.

How can drinking water be sterilised?

Chlorine, ozone or ultraviolet light.

What is desalination?

Removing dissolved salts from seawater/salty water to produce fresh water.

What two methods can desalinate water?

Distillation + membrane processes such as reverse osmosis.

What is a disadvantage of desalination?

It requires large amounts of energy.

Why is obtaining potable water from seawater generally harder than from fresh water?

Dissolved salts must be removed using energy-intensive processes.

What is waste water?

Water containing contaminants from homes, agriculture or industry.

Why must sewage be treated?

To remove organic matter + harmful microorganisms before release into the environment.

What may need removing from industrial waste water?

Organic matter + harmful chemicals.

What are the main stages of sewage treatment?

Screening/grit removal - sedimentation - anaerobic digestion of sludge - aerobic biological treatment of effluent.

What happens during screening and grit removal?

Large objects + grit are removed.

What happens during sedimentation?

Solids settle to form sewage sludge - liquid effluent remains above.

What happens to sewage sludge?

It undergoes anaerobic digestion.

What does anaerobic mean?

Without oxygen.

What happens to the effluent during sewage treatment?

It undergoes aerobic biological treatment.

What does aerobic mean?

In the presence of oxygen.

RP8 - What is the aim of the water practical?

Analyse + purify water samples from different sources.

RP8 - What properties of water samples are investigated?

pH + dissolved solids.

RP8 - How can pH be measured?

Using universal indicator or a pH probe.

RP8 - How can dissolved solids be investigated?

Evaporate a known amount of water + observe/measure the solid residue remaining.

RP8 - How can pure water be obtained from a water sample?

Simple distillation.

RP8 - Why does distillation purify water?

Water evaporates and is condensed separately - dissolved solids remain behind.

RP8 - What happens during simple distillation?

Heat sample - water vaporises - vapour passes into condenser - cools + condenses - purified water collected.

RP8 - Why should boiling chips/anti-bumping granules be used when heating?

Promote smooth boiling + reduce sudden bumping.

RP8 - Why should water samples from different sources be compared using the same volume?

Makes the amount of dissolved solid directly comparable.

Why are metal ores a finite resource?

They are being used much faster than they are naturally formed.

Why are alternative methods needed for extracting copper?

High-grade copper ores are becoming scarce.

What is phytomining?

Plants absorb metal compounds - plants are harvested + burned - ash contains metal compounds. (HT)

What is bioleaching?

Bacteria produce leachate solutions containing metal compounds from low-grade ores. (HT)

What is a leachate?

Solution containing dissolved metal compounds produced during bioleaching. (HT)

How can copper be obtained from solutions of copper compounds?

Displacement using scrap iron or electrolysis. (HT)

What is an advantage of phytomining and bioleaching?

Can extract metals from low-grade ores while avoiding much traditional mining. (HT)

What is a disadvantage of phytomining and bioleaching?

They can be slow + produce relatively small quantities. (HT)

What is a life-cycle assessment, LCA?

Assessment of environmental impacts of a product throughout its life.

What stages are considered in an LCA?

Raw material extraction/processing - manufacture/packaging - use - disposal, including transport/distribution.

What environmental factors can an LCA consider?

Use of water, resources + energy and production of waste/pollution.

Why is an LCA not completely objective?

Environmental effects can require value judgements when assigning their importance.

Which LCA factors are relatively easy to quantify?

Energy use, water use, resource use + amounts of waste.

Why can selective LCAs be misleading?

Stages/data can be chosen to support a predetermined conclusion.

How could an LCA be misused in advertising?

A company could select only favourable environmental impacts while ignoring others.

How should two products be compared using an LCA?

Compare environmental impacts at each life-cycle stage using available evidence/data.

What are three ways to reduce use of limited resources?

Reduce, reuse + recycle.

How does reducing material use help the environment?

Less raw material extraction, energy use, waste + environmental damage.

How does reusing products help?

Extends their useful life + reduces demand for new raw materials.

How does recycling help?

Reduces extraction of limited raw materials + often reduces waste.

How can glass be recycled?

Crushed + melted to make new glass products.

How can metals be recycled?

Melted + recast/reformed into new products.

Why must some materials be separated before recycling?

Different materials/compositions are needed for particular final products.

How can recycling steel reduce resource use?

Scrap steel can be added to iron from a blast furnace - reducing iron ore extraction.

What is corrosion?

Destruction of materials by chemical reactions with substances in the environment.

What is rusting?

Corrosion of iron.

What two substances are required for iron to rust?

Oxygen + water.

How can you experimentally show that water is needed for rusting?

Compare iron exposed to air + water with iron kept dry - only iron with both air and water rusts.

How can you experimentally show that oxygen is needed for rusting?

Compare iron in water containing oxygen with iron in boiled water protected from air - rust requires oxygen + water.

How can barrier methods prevent rusting?

Prevent oxygen + water reaching the iron.

Give examples of barrier methods.

Painting, greasing + electroplating.

Why does aluminium resist further corrosion?

It forms a protective aluminium oxide layer.

What is galvanising?

Coating iron/steel with zinc.

How does zinc provide sacrificial protection?

Zinc is more reactive than iron - zinc oxidises instead of the iron.

Why can galvanised iron remain protected even if scratched?

Zinc is more reactive and is sacrificed in preference to iron.

What is an alloy?

Mixture of a metal with one or more other elements.

Why are alloys often harder than pure metals?

Different-sized atoms distort regular layers - making it harder for layers to slide.

What is bronze?

Alloy of copper + tin.

What is brass?

Alloy of copper + zinc.

Why is gold jewellery usually an alloy?

Pure gold is soft - alloying makes it harder.

What does 24-carat gold mean?

100% pure gold.

What percentage gold is 18-carat gold?

75%.

What are steels?

Alloys of iron containing specific amounts of carbon and sometimes other metals.

What are the properties of high-carbon steel?

Strong + brittle.

What are the properties of low-carbon steel?

Softer + more easily shaped.

What is stainless steel?

Steel containing chromium + nickel.

What are the properties of stainless steel?

Hard + resistant to corrosion.

What is an important property of aluminium alloys?

Low density.

What are ceramics?

Materials including pottery and glass made from inorganic substances.

How are clay ceramics made?

Clay is shaped + heated in a furnace.

How is soda-lime glass made?

Heat a mixture of sand, sodium carbonate + limestone.

How is borosilicate glass made?

Heat sand + boron trioxide - it has a higher melting point than soda-lime glass.

What determines the properties of a polymer?

The monomers used + conditions under which the polymer is made.

What is a thermosoftening polymer?

Polymer that softens/melts when heated because there are no cross-links between chains.

What is a thermosetting polymer?

Polymer with cross-links between chains - does not soften when heated.

Why do thermosetting polymers not melt easily?

Strong covalent cross-links hold polymer chains together.

What is a composite material?

Material made by combining two or more materials to produce improved properties.

What are the two parts of a composite?

Matrix/binder + reinforcement.

Give examples of composite materials.

Fibreglass, carbon-fibre composites + concrete.

Why are composites useful?

Properties of different materials are combined to suit a particular purpose.

What is the Haber process used for?

Manufacture of ammonia.

What is ammonia mainly used to manufacture?

Nitrogen-based fertilisers.

What are the raw materials for the Haber process?

Nitrogen + hydrogen.