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25 Cards in this Set
- Front
- Back
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What properties of solids make them different to each other?
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Melting point Strength (compression - when pushed or tension -when pulled) Stiffness Hardness Density |
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What are properties of plastics, rubbers and fibres make them suitable for particular jobs?
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Plastic- washing up bowl commonly made of polythene: waterproof and easily melted into desired shape. Rubber- flexible and tough for bicycle tires. Fibres- tights made from nylon fibres: flexible and elastic. |
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What are the materials we use mixtures of and what do they include?
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Chemicals or mixtures of chemicals Include metals, ceramics and polymers |
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Where do the materials we use come from (give examples) ?
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Can be obtained (cotton, paper) or made from living things (silk, wool).
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What are synthetic materials?
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Alternatives to materials from living things
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What can be used to make synthetic materials?
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Raw materials from the Earth's crust
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In a chemical reaction, what must the atoms be?
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Same amount in the reactants as in the products
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What does crude oil mainly consist of?
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Hydrocarbons
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What are hydrocarbons?
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Chain molecules of varying lengths made from carbon and hydrogen atoms only
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What is most crude oil used as?
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Most used as fuels. Small percentage used for chemical synthesis.
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What does the petrochemical industry do?
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Refines crude oil by fractional distillation. Hydrocarbons separated into fractions of different boiling points. Produces fuels, lubricants and raw materials for chemical synthesis. |
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What is the relation between the size of molecules and size of forces between hydrocarbon molecules?
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Forces between molecules increase as the size of the molecule increases. Small molecules have weaker forces between them.
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As the forces between hydrocarbon molecules increases, what happens to the amount of energy needed for them to break out of a liquid and form a gas?
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It increases
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As forces between hydrocarbon molecules increases, what happens to the temperature at which the liquid boils?
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It increases as it is harder to break the bonds and requires more energy.
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What is the name of the small molecules that can join together to make long molecules called polymers?
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Monomers
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What happens when monomers join together?
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Polymers are formed |
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What is the name of the process in which monomers join to form polymers?
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Polymerisation
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What is polymerisation?
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When small molecules called monomers join together to form longer molecules called polymers.
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Recall an example of a material that, because of its superior properties, has replaced materials used in the past.
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Copper- used for plumbing in housing: malleable, not reactive with water (lead used before but compounds in water are toxic) |
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What do the properties of polymers depend on?
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How their molecules are arranged and held together.
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How do modifications in polymers produce changes to their properties?
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Increased chain length: stronger forces of attraction, stronger and less flexible material Cross-linking: make the material tougher and less flexible Using plasticisers: making the material softer and more flexible |
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What is meant by cross-linking?
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Chemical bonds can be formed to link together the chains of some polymers.
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What are plasticisers?
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Small molecules that can be added to polymers during their manufacture. They push the polymer molecules slightly further apart, weakening the forces between them.
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What does varying crystallinity do to properties of polymers?
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It is possible to make a polymer with the exact properties that are required for a particular purpose
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What is meant by varying crystallinity?
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Carefully controlling the amount of branching to make polymers with varying amounts of crystallinity.
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