Chemistry OCR, C2

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How can synthetic materials be produced?
by chemical synthesis
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What is chemical synthesis?
the process by which raw materials are made into useful products
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What materials can be obtained from living things?
cotton, paper, silk and wool
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What are alternative materials to natural materials?
synthetic materials
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What does crude oil mainly consist of?
hydrocarbons
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What are hydrocarbons?
chain molecules of varying lengths made from only carbon and hydrogen atoms
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What is crude oil used for?
a small percentage is used for chemical synthesis but most of crude oil is used for fuel
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How is crude oil separated?
by fractional distillation
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What is the process of fractional distillation?
crude oil is heated to remove all hydrocarbons, vapour enters the fractionating column at the bottom and cools as it rises, each fraction condenses to liquid and runs off. Remaining gas leaves at top
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What is the relation between the size of the forces between hydrocarbon molecules to the size of the molecules?
small molecules have week intermolecular forces and larger molecules have stronger intermolecular forces
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Why are different amounts of energy needed to break different hydrocarbon molecules?
the longer the hydrocarbon molecules, the stronger the intermolecular forces and stronger intermolecular forces need more energy to overcome them
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What is polymerisation?
the process where monomers can join together to make very long molecules called polymers
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What are the properties of natural rubber?
atoms within chains held together by covalent bonds but has weak forces between the molecules. Therefore the long polymer molecules can slide over each other making the material: stretchy, flexible and has a low melting point
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What are the properties of vulcanised rubber?
atoms within chains held together by covalent bonds but the molecules also have cross-links, making the material rigid and hard to stretch and has a high melting temperature
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What does increasing the chain length do to a polymer?
stronger forces between the molecules, making the material stronger
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What does cross-linking do to a polymer?
formed by atoms bonding between polymer molecules, so they can no longer move. Making a harder, stronger and stiffer material. (e.g vulcanisation: sulfur atoms form cross links between rubber molecules)
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What does the use of plasticizers do to a polymer?
makes polymer softer and more flexible because plasticizer is a small molecule that forces the chains apart, allowing the molecules to move more freely
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What does increased crystallinity do to a polymer?
packs molecules more closely together, to form a crystalline polymer. Intermolecular forces are stronger and so polymer is stronger, denser and has a higher melting point
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What is nanotechnology?
the use and control of structures that are very small (1-100 nanometres in size)
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How can nanoparticles occur?
naturally, by accident and by design
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Why do nanoparticles of a material show different prperties of large particles of the same material?
nanoparticles have a much larger surface area compared to their volume
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Why is there controversy around nanotechnology?
it is a new science and people are worried it hasn't been tested thoroughly. Therefore it may have harmful effects on the health.
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Card 2

Front

What is chemical synthesis?

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the process by which raw materials are made into useful products

Card 3

Front

What materials can be obtained from living things?

Back

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Card 4

Front

What are alternative materials to natural materials?

Back

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Card 5

Front

What does crude oil mainly consist of?

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