C10 - using resources

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137 Terms

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Melting point

The temperature at which a solid melts into a liquid

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Conductivity

How well a material conducts electricity

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Strength

The ability of a material to resist an applied force

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Hardness

How well a material can resist being scratched or indented

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Brittleness

How easily a material breaks when a force is applied

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Stiffness

How well a material can resist bending

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What are ceramics?

A group of hard, brittle, heat-resistant, and corrosion-resistant materials

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How are ceramics made?

By shaping and then firing a non metallic material, such a clay, at a high temperature

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What are two main groups of ceramics?

Clay ceramic and glass

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What are examples of clay ceramics?

Brick, china and porcelain

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How are clay ceramics made?

By shaping wet clay while it's soft and then heating it to a high temperature in a furnace, which causes it to harden

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Why can bricks be used for building?

Because they have a high compressive strength

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What type of glass is the glass we use most of?

Soda-lime glass

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How is soda lime glass made?

by melting a mixture of sand (silicon oxide), sodium carbonate and limestone, then allowing the molten liquid to cool and solidify.

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How is borosilicate glass made?

By heating sand with boron trioxide - has a much higher melting point than soda lime glass

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Why is glass useful for windows?

It is transparent, strong, and a good thermal insulator

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Composite material

Consists of two or more materials with different properties that have been combines to produce a material with more desirable properties

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What two components are most composite materials made from?

The reinforcement and the matrix

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What is the reinforcement?

Long solid fibres or fragments

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What is the matrix?

Binds the reinforcement together - usually something that starts soft and then hardens

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Polymers

Large molecules of high relative molecular mass and are made by linking large numbers of smaller molecules called monomers

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What does the properties of a polymer depend on?

The monomers from which it was made and the conditions of the chemical reaction

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What are the properties of polymers?

flexible, easily shaped, and good insulators of heat and electricity.

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What two main forms does poly(ethene) come in?

- low density poly(ethene) LDPE

- high density poly(ethene) HDPE

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What are the conditions to make LDPE?

- moderate temperatures

- high pressure

- catalyst

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What are the properties of LDPE?

More flexible but weaker

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What are the uses of LDPE?

Carrier bags

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What are the conditions to make HDPE?

- low temperature

- low pressure

- catalyst

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What are the properties of HDPE?

More rigid and stronger

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What are the uses of HDPE?

Drainpipes

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Thermosoftening polymers

- Lots of polymer chains held together by weak intermolecular forces

- these break easily when heated causing the polymer to melt

- it can then be remoulded into a different shape and will harden again when cooled

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Thermosetting polymers

- made from lots of polymer chains held together by strong covalent bonds

- these require lots of energy to break so dont soften when heated

- these polymers are hard, strong and rigid

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What are the properties of metals?

Malleable, ductile, good to conductors of heat/electricity, high mp and bp

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What are alloys?

Metals with atoms of another element mixed - much stronger than pure metals

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What are alloys useful for?

Purposes where they might be put under stress like in buildings

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Corrosion

The process by which metals are slowly broken down by reacting with substances in their environment

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Example of corrosion

Rusting of iron

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Equation for the rusting of iron

Iron + oxygen + water —-> hydrated (iii) iron oxide

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What happens at the atomic level to the iron during rusting?

The iron atoms are each losing 3 electrons to become iron 3+ ions

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What happens at the atomic level to the oxygen during rusting?

The 2 oxygen atoms in each molecule are gaining two electrons to become o2- ions

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Why is the reaction of the Rusting of iron a redox reaction?

The iron becomes oxidised as it loses 3 electrons

The oxygen becomes reduced as it gains 2 electrons

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What needs to be present for rusting to take place?

Water and oxygen

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Why is it only the surface of a metal that corrodes?

It is only the surface that is exposed to the substances in the environment

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Why can the entire chunk of iron break down eventually by rust if left long enough?

Each layer flakes off revealing a new layer which will also flake off

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What happens when metals like aluminium corrode?

Only the surface atoms are affected - forms a protective layer of aluminium oxide which protects the rest of the metal from the environment

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How can we prevent iron from rusting?

Barrier methods and sacrificial methods

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How do barrier methods work?

By preventing oxygen and water from touching the iron so that rusting can't take place

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What are examples of barrier methods?

Painting, oil/grease, electroplating

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How do sacrificial methods work?

Adding a more reactive metal like aluminium or zinc to the iron means that if the object is exposed to oxygen, the more reactive metal will be oxidised instead

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What is an example of preventing rust that uses both barrier and sacrificial methods?

Galvanising - coating the iron object in a layer of zinc

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What is meant by sustainable?

Meets the needs of current generations without jeopardising the lives of future generations

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What is one way we can develop more sustainably?

By using renewable resources rather than finite resources

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What are ways to reduce the environmental impact of the manufacturing process?

- making processes more efficient

- using catalysts to reduce the amount of energy used

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What is the most sustainable thing to do once we've finished using a product?

Reusing and recycling

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Life Cycle Assessment (LCA)

An assessment of the different stages in a products life cycle in order to assess its impact on the environment

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What are the 4 main stages of LCAs?

- extracting an processing the raw materials

- manufacturing and packaging your product

- using your product

- disposing of it

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How does extracting raw materials damage the local environment?

- cutting down forests

- mining

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How does processing raw materials indirectly damage the environment?

- huge amounts of energy are required for extracting metals from their ores or the fractional distillation of crude oil

- pollutants can be released

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What are the 3 main problems associated with manufacturing and packaging?

- energy use

- pollution

- waste products

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What can be done with waste products if they aren't disposed of?

They can be used as raw materials for something else

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What needs to be considered when assessing the impact of using a product?

- how much damage it does during its lifetime e.g. pollution

- how long the product is used for

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What is wrong with using landfills?

- takes up space that could've been used for nature

- chemicals might seep out into the surrounding ecosystems

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Why is burning waste bad?

Releases pollutants into the atmosphere

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What is the raw material for plastic bags?

crude oil needs to be separated by fractional distillation - uses high amounts of energy

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What is the raw materials for paper bags?

Wood from trees - reduces habitat available for animals and plants

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How are plastic bags manufactured?

Hydrocarbons from fractional distillation are cracked to make alkenes which undergo polymerisation to make plastics

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How are paper bags manufactured?

Timber has to be pulped - requires loads of energy, produces waste

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Can plastics bags be reused multiple times?

Yes

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Can paper bags be reused multiple times?

No

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How are plastic bags disposed of?

Not biodegradable, take up space in landfills, can get out into the wild and harm animals

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How are paper bags disposed of?

biodegradable, non-toxic and can be recycled

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Why is the manufacture of products involving loads of different steps a limitation of lifecycle assessments?

- it is almost impossible to quantify all of the steps

- it is difficult to assess the harm of each step

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Why is the fact that LCAs are so complex a limitation of LCAs?

- they can be manipulated to deliberately support a company (positive advertising)

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Potable water

water that is safe to drink

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What is pure water?

contains only water molecules (boils at exactly 100'C)

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Why isn't potable water pure water?

It contains dissolved substances

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What are the 3 criteria for water to be considered potable?

- levels of dissolved substances need to be fairly low

- has to have a pH between 6.5 and 8.5

- no microorganisms

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What does the source of potable water depend on?

Where in the world you live

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Where is water in the UK obtained?

- from the rain, collected as groundwater or surface water

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What are examples of surface water sources?

Lakes, rivers, reservoirs

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What are examples of ground water sources?

Aquifers - areas of permeable rock underground and trap water

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Benefits of using surface water

- easy to access

- gets replaced frequently by the rain

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Why is ground water relied on instead in hotter areas of the UK?

If its hot and sunny, surface water can dry up as it is exposed to the sun

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How is water treated?

- fresh water is passed through a wire mesh to filter big things

- passed through a bed of sand and gravel to filter out smaller bits

- sterilised to kill harmful microbes

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How is water sterilised?

- bubbling chlorine gas

- exposing to ozone or ultraviolet light

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Desalination

A process of removing salt from ocean water

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What are the two main techniques for desalination?

Distillation and reverse osmosis

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Why are the processes of distillation and reverse osmosis somewhat impractical for producing large amounts of water?

- requires a lot of energy so expensive

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How is water desalinated by distillation?

- water is boiled

- water vapour is condensed and collected to give us pure distilled water

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How is water desalinated by reverse osmosis?

Salty water is passed through a membrane which only allows water molecules to passed through minerals and ions get trapped and separated leaving pure distilled water

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What are the 3 main sources of waste water?

Domestic, agricultural systems and industrial

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What are examples of domestic waste?

Waste from showers, sinks, toilets

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What are examples of agricultural waste?

Nutrient run off, animal waste

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What is an example of industrial waste?

Waste from factories that use/make chemicals

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How does sewage treatment work?

- (screening) the sewage is passed through gratings and meshes to remove anything large

- (sedimentation) the sewage is left to sit in a settlement tank so that the heavier particles settle at the bottom as sludge whilst the lighter particles settle at the top as effluent

- air is pumped through the effluent to supply the bacteria with oxygen to undergo aerobic digestion

- the sludge is sealed in a container to prevent entry of air which ensures anaerobic respiration

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What are the other uses for sludge once it has been digested?

Releases methane gas from the anaerobic digestion so can be burnt as a fuel, can be used as fertiliser as it contains many nutrients

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How can toxic chemicals in sludge be removed?

By adding chemicals to precipitate out any metals or using uv radiation

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Why do some countries rely on treating waste water rather than desalinating salt water?

As it is easier

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How is the ammonia made from the haber process used?

Used as a starting material for fertilisers, dyes, explosives

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Where is the nitrogen used in the haber process obtained?

From the air