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44 Cards in this Set
- Front
- Back
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What needs to be considered when deciding what material to use for a specific job?
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The different properties, e.g. soft, hard, high boiling point, strength, stiffness and density etc.
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Give an example of a synthetic material.
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Neoprene wetsuits, plastic washing up bowls or Kevlar body armour.
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Why do materials need to be measured many times?
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Because they vary slightly so if they are measured more times then it is possible to work of the range, eliminate outliers in the data, find out the mean, and estimate the true value.
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What are synthetic materials made from?
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They are made from natural materials that have come from the Earth's crust.
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Give an example of a synthetic material that has come from the Earth's crust.
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Plastic from crude oil or aluminium metal from bauxite ore.
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What do natural polymers come from?
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Natural living things on Earth.
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Give an example of a natural material.
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Cotton from plants, silk from animals and limestone/iron ore from the Earth's crust.
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What are synthetic materials?
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Alternatives to using natural materials.
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What is crude oil made up of?
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Hydrocarbon chains of varying lengths. Hydrogen and carbon only!!
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How is crude oil separated into fractions?
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Fractional distillation.
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What does each fraction contain?
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A small range of molecule sizes with similar boiling points.
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What do larger hydrocarbons have?
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More attractive forces between them so it means that more energy is needed to separate them. This results in higher boiling points.
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What are most fractions used for?
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Mainly fuels and lubricants. However, a small amount is used for raw materials such as plastics and other synthetic materials.
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What do the properties of a plastic link to?
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The amount of energy needed to separate the chains.
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What can small molecules (monomers) do?
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They can join together to make polymers.
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What does polymer strength depend on?
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It depends on chain length, cross-linking, plasticizers and increased crystallinity.
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What does nanotechnology involve?
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Small structures of up to 100nm in size. They occur naturally, by accident or by design.
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What do nanoparticles have?
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Different properties compared to larger particles of the same material. A key factor is their larger surface area compared to their volume.
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What can carbon nanoparticles be used for?
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To strengthen sports equipment and body armour.
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What do silver nanoparticles do?
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Give fibres antibacterial properties.
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What is the problem with using nanoparticles?
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The health effects are unknown as they have not been around for long enough to be studied that deeply.
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Describe low density polyethene.
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Long molecules with small branches to keep the molecule chains apart, this means the forces between the molecules are weak.
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Give an example of low density polyethene.
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Plastic carrier bags are weak, flexible, soft and have low melting points.
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Describe high density polyethene.
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Has long chains but no branches, the molecules are aligned close to each other. This means there is more attraction force between the molecules. This means it is stronger and is used to make long-lasting items which are hard and stiff.
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Give an example of a HDPE.
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Water pipes.
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What does HDPE have?
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A high degree of crystallinity, meaning there are many areas with regular patterns in the way the molecules are lined up.
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What are high crystalline polymers?
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They are strong,"", have high melting points but can be brittle.
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What are plasticizers used for?
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To make a material softer. they are small molecules which are inserted into polymer chains to keep them apart. this weakens forces between them.
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What do Thermoplastics do when heated?
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They get softer and can be moulded into other shapes.
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What do thermosetting plastics do?
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They do not soften when heated. They contain cross-links which lock molecules together so they do not melt as easily.
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How can crystallinity be increased?
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By removing branches on the main polymer chain and making the chains as flat as possible. this is so that the molecules can line up neatly.
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What are nanoparticles useful for?
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They are effective catalysts as they have a large surface area. Increasing surface area provides more sites for reactions to take place.
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What does nanotechnology build?
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Structures from 10 atoms across up to a thousand atoms across.
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What happens in fractional distillation?
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1: The oil is heated and turned into gases
2: The tower gets cooler as it gets higher 3: Gas molecules condense into liquids when they cool 4:Liquids with similar boiling points collect together into fractions. |
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What is a polymer?
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A large molecule made by joining monomers. A polymer can have a chain of anything from hundreds to millions of carbon atoms.
it is made by polymerization. |
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How can polymers be altered?
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They can replace hydrogen atoms with other atoms or groups of atoms.
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Give an example of a type of nanoparticle and how it is used.
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Titanium oxide nanoparticles are put in sunscreen and make it transparent. they also help to absorb the UV light.
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What are nanoparticles that are mixed with other materials, e.g. metals called?
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Composites.
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What properties do composites have?
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Strong & hard wearing.
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What do plasticizers do?
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They soften a polymer. They are small molecules inserted into polymer chains to keep them apart which weakens the forces between them.
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How can crystallinity be increased?
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By removing braches from the main polymer chain and making the chains as flat as possible. This means that the molecule chains are able to line up neatly.
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What does drawing polymers through a tiny hole when heated do?
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It makes the molecule chains line up which increases the crystallinity and forms a high tensile fibre.
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What is vulcanization?
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Vulcanization was first discovered by Charles Goodyear. He discovered that it makes a polymer more hard wearing. Without the cross-linking process, the longer the chains move too easily and uncoil, meaning they slide past each other.
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What is the process of vulcanization?
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Sulphur atoms form cross-links across the polymer chains. This stops the chains from sliding past each other.
Vulcanization means that is strengthens the forces between the molecules. |
