Chemistry 10. Using Resources

What is the scientific definition of 'sustainable development'?

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

Resources that are being used up faster than they can be replaced, such as fossil fuels, are described as _ resources.

finite

How are finite resources from the Earth, oceans, and atmosphere processed?

They are processed to provide energy and materials.

What is the definition of 'potable water'?

Water that is safe for human consumption.

True or False: Potable water is chemically pure water.

False, because it contains dissolved substances.

In the UK, what is the typical source of 'fresh water' used to produce potable water?

Ground water from aquifers or surface water from rivers and lakes.

What is the purpose of passing fresh water through filter beds during treatment?

To remove insoluble solids.

Identify three agents used to sterilise fresh water to kill microbes.

Chlorine, ozone, or ultraviolet (UV) light.

The process of removing salt from sea water to make it potable is known as _.

desalination

What are the two main methods used for the desalination of salty water?

Distillation and reverse osmosis.

Why are desalination processes not always the preferred method for producing potable water?

They require large amounts of energy.

What method of desalination uses membranes to separate salts from water?

Reverse osmosis

In waste water treatment, what is the first stage used to remove large grit and solids?

Screening

During the sedimentation of sewage, what two substances are produced?

Sewage sludge (which sinks) and effluent (which floats).

By what process is sewage sludge broken down by bacteria in the absence of oxygen?

Anaerobic digestion

What is produced by the anaerobic digestion of sewage sludge that can be used as fuel?

Biogas

How is the liquid effluent treated during waste water processing?

By aerobic biological treatment (treated with air to allow bacteria to break down organic matter).

Why is the treatment of industrial waste water often more complex than domestic sewage?

It may require the removal of harmful chemicals and organic matter.

As high-grade copper ores become scarce, which biological method uses plants to absorb metal compounds?

Phytomining

In phytomining, how is the metal eventually obtained from the plants?

The plants are harvested and burned; the ash contains the metal compounds.

What is 'bioleaching'?

The use of bacteria to produce leachate solutions that contain metal compounds.

After phytomining or bioleaching, name two ways copper can be obtained from solutions of copper compounds.

Displacement (using scrap iron) or electrolysis.

Why is using scrap iron to displace copper from solutions a sustainable choice?

It uses a cheap, recycled material and requires less energy than primary extraction.

What does an LCA (Life Cycle Assessment) assess?

The environmental impact of a product throughout its entire life.

List the four stages of a product's life cycle evaluated in an LCA.

1. Extracting raw materials, 2. Manufacturing/packaging, 3. Use/operation, 4. Disposal.

Why is an LCA not a purely objective process?

Allocating numerical values to pollutant effects requires value judgements.

How can abbreviated or selective LCAs be misused?

They can be used to reach pre-determined conclusions, such as for advertising purposes.

Name three environmental benefits of recycling materials like metals and glass.

Reduces use of limited resources, reduces energy consumption, and reduces waste/landfill.

How is glass typically recycled?

It is crushed and melted to be remoulded into new glass products.

How are metals typically recycled?

They are melted and recast or reformed into different products.

What is 'corrosion'?

The destruction of materials by chemical reactions with substances in the environment.

What two substances must be present for iron to rust?

Air (oxygen) and water.

Why does aluminium not corrode away as quickly as iron, despite being reactive?

It has an oxide coating that protects the metal from further corrosion.

How does greasing or painting prevent the corrosion of iron?

It acts as a barrier to prevent air and water from reaching the surface of the metal.

What is 'sacrificial protection'?

Using a more reactive metal to protect a less reactive one (the more reactive metal oxidises instead).

What term describes the process of coating iron with zinc for protection?

Galvanising

Why do alloys tend to be harder than pure metals?

Different sized atoms distort the regular layers, making it harder for them to slide over each other.

Bronze is an alloy of copper and which other metal?

Tin

Brass is an alloy of copper and which other metal?

Zinc

If a piece of gold jewellery is 18 carats, what percentage of it is pure gold?

75% (Calculation: $\frac{18}{24} \times 100$).

Which type of steel is strong but brittle?

High carbon steel

What are the two main alloying elements added to iron to make stainless steel?

Chromium and nickel.

Most of the glass we use is _ glass, made from sand, sodium carbonate, and limestone.

soda-lime

How does borosilicate glass differ from soda-lime glass in terms of properties?

It melts at higher temperatures.

What are the raw materials for making borosilicate glass?

Sand and boron trioxide.

How are clay ceramics, such as bricks or pottery, made?

By shaping wet clay and then heating it in a furnace.

The properties of polymers depend on the monomers they are made from and the _ under which they are made.

conditions

Which type of polymer melts when heated because it lacks cross-links between chains?

Thermosoftening polymers

Why do thermosetting polymers not melt when heated?

They have strong cross-links (covalent bonds) between polymer chains.

What is a 'composite' material?

A material made of two substances: a matrix/binder and a reinforcement (fibres or fragments).

In the context of carbon fibre composites, what is the 'reinforcement'?

Carbon fibres

What is the primary industrial use of the Haber process?

To manufacture ammonia ($NH_{3}$).

Identify the two raw materials needed for the Haber process.

Nitrogen and hydrogen.

In the Haber process, where is the nitrogen obtained from?

The air

In the Haber process, where is the hydrogen typically obtained from?

Natural gas (containing methane).

What temperature is typically used for the Haber process?

$450^{\circ}C$

What pressure is typically used for the Haber process?

200 atmospheres

What catalyst is used in the Haber process?

Iron

Write the balanced symbol equation for the Haber process.

$N{2}(g)+3H{2}(g)\rightleftharpoons2NH_{3}(g)$

Why is the ammonia produced in the Haber process cooled?

To liquefy it so it can be removed from the reaction mixture.

What happens to the unreacted nitrogen and hydrogen in the Haber process?

They are recycled back into the reactor.

Explain the trade-off regarding pressure in the Haber process.

High pressure increases yield but is expensive and dangerous to maintain.

Why is $450^{\circ}C$ considered a 'compromise' temperature in the Haber process?

The forward reaction is exothermic, so lower temperatures increase yield but make the reaction too slow.

What three elements are provided by NPK fertilisers?

Nitrogen (N), phosphorus (P), and potassium (K).

What is the result of reacting ammonia with nitric acid?

Ammonium nitrate (a nitrogen-rich salt).

Why can phosphate rock not be used directly as a fertiliser?

It is insoluble in water.

What salt is produced when phosphate rock is treated with nitric acid?

Calcium nitrate (and phosphoric acid is also produced).

Treating phosphate rock with sulfuric acid produces 'single superphosphate', which is a mixture of and .

calcium phosphate and calcium sulfate

What is the product of reacting phosphate rock with phosphoric acid?

Triple superphosphate (calcium phosphate).

Contrast industrial and laboratory production of ammonium sulfate in terms of scale.

Industrial production is large-scale, while laboratory production is small-scale.

Contrast industrial and laboratory production of ammonium sulfate in terms of process type.

Industrial is a continuous process; laboratory is a batch process.

In Required Practical 8 (Water Purification), how can you test for the presence of dissolved solids in a water sample?

Weigh an evaporating basin, evaporate a fixed volume of water to dryness, and reweigh to find the mass of the residue.

How can you determine if a water sample is 'pure' water in the chemical sense using boiling point?

Pure water will boil at exactly $100^{\circ}C$ at standard pressure.

What is the 'matrix' in a composite material like reinforced concrete?

The cement/concrete

Why does high-density poly(ethene) (HDPE) have a higher density than low-density poly(ethene) (LDPE)?

HDPE has straighter chains that pack closer together, whereas LDPE has branched chains.

What happens to the 'effluent' during sewage treatment?

It undergoes aerobic biological treatment and is then released back into the environment.

Which metal is used to protect iron from rusting in 'sacrificial protection' because it is more reactive?

Zinc (or Magnesium)

What is the name of the mixture produced when phosphate rock reacts with sulfuric acid?

Single superphosphate

In the context of LCAs, why is 'disposal' a complex stage to evaluate?

It involves transport, space in landfill, or energy/pollution from incineration or recycling.

Identify one renewable resource used to supplement or replace a natural product.

Timber (used for construction instead of metal or plastic).