C2 - Material Choices

What process is used to refine crude oil?
Fractional Distillation
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What happens in fractional distillation?
The crude oil is heated in a furnace to around 400°C. This allows all of the hydrocarbons in the crude oil to move into the bottom of the fractionating tower. The tower is hottest at the bottom and coolest at the top
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Which molecules move to the top of the tower and why?
The smallest molecules contained in the crude oil have lower boiling points and so move to the top of the tower. This is because the forces between these molecules are weak, so little energy is required to vaporise them.
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Which molecules remain near the bottom of the tower and why?
Larger molecules will remain lower down the tower as they have higher boiling points. This is because forces between the molecules are stronger.
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What happens to the boiling point of a hydrocarbon as the number of carbon atoms increases?
The boiling point of hydrocarbons increases as the number of carbon atoms in the molecule increases. This is because forces between molecules increase as the size of the molecule increases.
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What is polymerisation?
Some small molecules (monomers) can join together to make very long molecules called polymers. This process is called polymerisation.
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How do forces affect the boiling point of a solid?
The stronger the forces between the particles, the more energy is needed to break the particles out of the solid structure. The more energy that is needed, the higher the melting point of the solid.
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How are some materials flexible?
Many polymers, such as poly(ethene), contain long molecules that lie side by side. These can uncoil and slide past each other, making the material flexible.
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Why do longer polymer chains make stronger and more flexible materials?
Long polymer chains have stronger forces of attraction than shorter ones.
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What are plasticisers?
Plasticisers are small molecules that can be added to polymers during their manufacture. They push the polymer molecules slightly further apart, weakening the forces between them and making the material softer and more flexible.
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What do cross links do?
Chemical bonds can be formed to link together the chains of some polymers. These cross-links make the material tougher and less flexible.
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What is nanotechnology?
Nonoparticles are measured in nanometres (nm). A nanometre is one billionth of a metre (0.000 000 001m). Nanotechnology is concerned with the use and control of structures that are 1-100 nanometres in size.
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What is the difference between a nanoparticle and a larger particle of the same material?
Nanoparticles of a material show different properties compared to larger particles of the same material. Forces of attraction between surfaces can appear to be weak on a larger scale, but on a nanoscale they are strong.
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Why are the forces of attraction between surfaces stronger for nonoparticles?
One reason for this is the surface area to volume ratio. In nanoparticles this is very large. Atoms on the surface of a material are often more reactive than those in the centre, so a larger surface area means the material is more reactive.
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What is one use of nanoparticles?
sports equipment: nanoparticles are added to materials to make them stronger whilst often being lighter. They have been used in tennis rackets, golf clubs and shoes
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What is another use of nanoparticles?
healthcare: nanoparticles are used in sunscreens. They offer protection and can be rubbed in so there are no white marks.
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Are there any harmful effects from nanoparticles?
There are some concerns that nanoparticles may be toxic to people. They may be able to enter the brain from the bloodstream and cause harm. Some people think more tests should take place before nanoparticles of a material are used on a wider scale.
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Other cards in this set

Card 2

Front

What happens in fractional distillation?

Back

The crude oil is heated in a furnace to around 400°C. This allows all of the hydrocarbons in the crude oil to move into the bottom of the fractionating tower. The tower is hottest at the bottom and coolest at the top

Card 3

Front

Which molecules move to the top of the tower and why?

Back

Preview of the front of card 3

Card 4

Front

Which molecules remain near the bottom of the tower and why?

Back

Preview of the front of card 4

Card 5

Front

What happens to the boiling point of a hydrocarbon as the number of carbon atoms increases?

Back

Preview of the front of card 5
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