C2

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What are materials?
Chemicals or mixtures of chemicals.
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Where do some materials come from?
Living things (e.g. cotton and paper)
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How are synthetic materials produced?
By chemical synthesis
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How can synthetic materials be made?
As alternatives, starting from materials extracted from the Earth's crust.
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What does the petrochemical industry refine crude oil for?
To produce fuels, lubricants and raw materials for chemical synthesis.
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What proportion of crude oil is used for chemical synthesis and what is used for fuels?
Small proportion for chemical synthesis, majority for fuels.
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What is crude oil?
A raw material found in the Earth's crust. Is a thick black liquid made from hydrocarbons.
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What are hydrocarbons?
Compounds made from only carbon and hydrogen atoms.
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What kind of molecules do hydrocarbons have?
Some have small, some have longer chain molecules.
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How is crude oil separated?
By fractional distillation into useful fractions
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What are the boiling points like of hydrocarbons in a fractions?
They have similar boiling points.
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Why do different fractions have different boiling points?
So fractions in crude oil can be separated by fractional distillation.
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What is the process of fractional distillation?
Crude oil heated to evaporate all hydrocarbons. Vapour passes into fractionating column near bottom and cools as it rises. Each fractions condenses to liquid+runs off when cooled below boiling point.Remaining gases leave @ top+used as gaseous fuels.
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What are the fractions of the fractional distillation tower+ what are they used for (going from lowest - so hottest, to highest - so coolest)?
Bitumen (tar for roofs and roads), fuel oil (fuel for power stations/ships), diesel (fuel for cars/lorries/buses), kerosene/paraffin (aircraft fuel), naphtha (making other chemicals), petrol (fuel for cars), refinery gases/LPG (bottled gas)
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What is the coldest and the hottest point in a fractional distillation tower?
Coldest = approx 25 degrees Celcuis Hottest = approx 350 degrees Celcius
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What happens to the molecule size, boiling point, evaporation ease and how easy the hydrocarbons burn the further (hotter) you go down the tower?
Become larger molecules, higher boiling point, harder to evaporate, doesn't burn as easily.
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What are intermolecular forces?
The forces between molecules that hold them together in a solid or liquid.
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How do the length of the hydrocarbon molcules affect the strength of the intermolecular forces?
Longer molecules = stronger forces
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How do the strength of intermolecular forces affect the boiling point of the hydrocarbons?
Stronger forces need more energy to overcome them, so a higher temp is needed to boil the longer hyrocarbon fractions.
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What are the different properties of solid materials/
Different melting points and densities, can be strong or weak (in tension or compression), can be rigid or flexible, hard or soft, will be better suited to some uses.
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What will the properties of materials used affect?
The durability+effectiveness of a product.
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Why do manufacturers test and assess the materials carefully beforehand?
To see their durability and effectiveness.
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What are the properties+ uses of unvulcanised rubbers/vulcanised rubbers/plastic-polythene?
Low tensile strength+soft,flexible,elastic. Erasers, rubber bands./High tensile strength+hard,flexible,elastic. Car tyres, conveyor bets, shock absorbers./Lightweight (low density), flexible and easy moulded. Plastic bags, moulded containers.
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What are the properties and uses of plastic-polystyrene/synthetic fibres-nylon?
Lightweight(low density), stiff, good thermal insulator as a foam, water resistant. meat trays, egg cartons, coffe cups, protecting appliances+electronics./lightweight(low density), tough+waterproof, blocks ultraviolet light. Clothing, climbing ropes
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What are the properties and uses of synthetic fibres- polyester?
Lightweight (low density), tough and waterproof. Clothing, bottles.
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What is polymerisation?
An important chemical process in which small hydrocarbon molecules (monomers) are joined together to make very long molecules (polymers).
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What is polymer poly(ethene), aka polythene, made from?
Ethene monomers.
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What must the number of atoms be in a chemical reaction?
The number of atoms in each element in products must be same as in the reactants.
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What can chemists produce by choosing different monomers for the polymerisation process?
A range of polymers with different properties.
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What are the properties and uses of the polymer of chloroethene/tetrafluoroethene?
Rigid and resistant to UV light, used for window frames/ very slippery, high melting point+chemically unreactive. Used for non stick frying pans.
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What can polymerisation be used to create?
A wide range of different materials which have different properties, meaning that they can be used for different purposes.
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Why have many traditional (natural) materials been replaced by polymers?
Because of their superior properties.
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What is are examples of a natural material being replaced by polymers?
Carrier bags used to be made of paper but now made from polythene as it is stronger+waterproof. Windo frames were mae of wood but now often made from polychloroethene as it is unreactive+doesn't rot.
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What do the properties of solid materials depend on?
How theur particles are arranged and held together.
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What are the molecules and atoms like in natural rubber?
Is a mass of long chain molecules. Atoms within chains held together by strong covalent bonds, but very weak forces between molecules. The long polymer molecules can slide over one another+the material can stretch.
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What are the properties of natural rubber?
Is very flexible and has a low melting point because little energy is needed to separate the molecules.
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What are the molecules and atoms like in vulcanised rubber?
Is a mass of tangled molecules where atoms within chains are held together by strong covalent bonds. Molecules have cross links which are strong covalent bonds between long chain molecules.
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What are the properties of vulcanised rubber?
Quite rigid and hard to stretch as molecules won't slide over each other. Needs lots of energy to separate molecules and has a high melting temp.
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What can modifications also produce?
Changes to the properties of polymers
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What does increasing the chain length do?
Means there's morecontact and therfore stronger forces between the molecules, which makes the plastic stronger.
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How are cross links formed? What do they do?
Formed by atoms bonding between polymer molecules, so they can no longer move. Makes a harder, stronger and stiffer material.
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What is an example of cross linking?
Vulcanisation-when sulfur atoms form cross links between rubber molecules. Vulcanised rubber is used to make car tyres and conveyor belts.
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What does adding plasticizers to a polymer do?
Makes polymer softer+more flexible
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What is a plasticizer?
A small molecule that sits between molecules and forces the chains apart.
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What is the effect of plasticizers?
Makes forces between chains weaker so molecules can move more easily.
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Where is plasticized PVC and unplasticized PVC used?
Plasticized = used in children's toys. Unplasticized = used in window frames.
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How can you form a crystalline polymer?
By packing molecules closer together
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What are the effects of making polymers more crystalline?
Intermolecular forces are slightly stronger so polymer is stronger, denser and has a slightly higher melting point.
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What is a nanometre?
One millionth of a millimetre - the width of a few atoms
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How can nanoscale particules occur and how can they be made?
Can occur naturally (e.g. sea spray), occur as an accidental result of human activity (e.g. particulate carbon released when fuels burn). Can be made deliberately by scientists.
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What is nanotechnology?
The production, study and control of tiny particles on a nanoscale (1 to 100 nanometres).
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Why do nanoscale particles have different properties to larger particles?
Because the smaller particles have a much larger surface area.
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How can nanoparticles be used to modify the properties of the other materials, especially polymers?
Silver nanoparticles can be used to give fibres in clothes antibacterial properties which can help socks from smelling. Adding carbon nanotubes to sport equipment like tennis rackets+golf clubs can make them lighter, stiffer, stronger.
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What are some concerns that people have about nanotechnology?
Some worried that these new materials haven't been thoroughly tested and could lead to health problems in the future.
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What happens to claims made by one scientist before they are accepted by the scientific community?
They are critically evaluated by other scientists.
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Other cards in this set

Card 2

Front

Where do some materials come from?

Back

Living things (e.g. cotton and paper)

Card 3

Front

How are synthetic materials produced?

Back

Preview of the front of card 3

Card 4

Front

How can synthetic materials be made?

Back

Preview of the front of card 4

Card 5

Front

What does the petrochemical industry refine crude oil for?

Back

Preview of the front of card 5
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