how much a material can be stretched before breaking
3 of 40
define compressive strength
how much a material can be compressed before breaking
4 of 40
what is density
mass per unit of volume
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what is an incorrect result often referred to as
an outlier
6 of 40
what do errors in measurements cause
variation in data
7 of 40
give the properties of a metal
hard, shiny, malleable, good electrical conductors
8 of 40
give the properties of ceramics
hard, strong
9 of 40
give three natural materials that are taken from the earth
curde oil, coal, limestone
10 of 40
what is a synthetic material
materials that are manufactured by chemical reactions using raw materials
11 of 40
why have synthetic materials replaced some natural materials
natural materials are on a short supply, they can be specifically designed, cheaper and bigger quantities
12 of 40
what is crude oil
a mixture of thousands of hydrocarbons
13 of 40
what is a hydrocarbon
a compound made from hydrogen and carbon only
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how much of crude oil is used as fuel
90%
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what is approx 3% of crude oil used for
synethise other chemicals
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how is crude oil separated
fractional distillation
17 of 40
explain fractional distillation
the oil is heated so it turns into a gas, the tower is cooler at the top, gas molecules condense and liquids with similar boiling points collect together
18 of 40
what happens when hydrocarbon chain length increases
force between the molecules increase
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why do some molecules have higher boiling points
they are larger,so need more energy to break them apart
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what is a polymer
a large molecule made from smaller molecules called monomers
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how is a polymer made
polymerisation
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How can polymer chains be altered
replacing hydrogen atoms with other atoms
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what does it mean if a polymer is high crystalline
high melting points, brittle
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what are plasticisers
small molecules, inserted into polymer chains to keep them apart, making them more flexible
25 of 40
how can crystallinity be increased
removing branches and making the chains flatter
26 of 40
how do nanoparticles occur
naturally (salt in Seaspray), accidentally (solid particles when fuels burn)
27 of 40
what are nanoparticles
materials containing up to a thousand atoms
28 of 40
what is nanotechnology
the use and control of very small structures
29 of 40
why are some nanoparticles catalysts
they have a large surface area so more reactions can take place
30 of 40
nanoparticles show different properties to larger particles of the same material, why
they have larger surface areas
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why is titanium oxide nanoparticles put into sunscreen
it absorbs UV light
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why are silver nanoparticles put into food containers, wound dressings and fibres
they kill bacteria
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what is a composite
materials like ceramics and metals mixed with nanoparticles
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what are the properties of composites
stronger, hardwearing
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what are graphite sheets
one-atom thick sheets, called graphene sheets
36 of 40
what happens if silver nanoparticles get into sewage
it can kill the bacteria that is in there to clean the water
37 of 40
what is one fear of nanoparticles in the air
if breathed in, they could cause lung or brain damage
38 of 40
what do people want proof of hat nanotechnology will not do
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