1. 26/04/2017
26/04/2017
C2 Material Choices
This PowerPoint supports the C2 topic from the 2011 OCR 21st Century course

2. Hydrocarbons and crude oil
26/04/2017
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Increasing length C H
These different “lengths” are called “_______” and most of them are used as _____. Some are used to make materials such as _______. Longer chains have higher _____ points.
Ethane
Butane C H
Words – boiling, fractions, plastics, fuels

3. Fractional distillation
26/04/2017
Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:
Fractions with low boiling points condense at the top
Fractions with high boiling points condense at the bottom

4. Forces between molecules
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Weak force of interaction here
Longer molecules = stronger force of attraction, leading to higher boiling points due to the molecules needing more energy to “pull” them away from each other.

5. Polymers
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Ethene
Here’s ethene. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…
Step 1: Break the double bond
Step 2: Add the molecules together:
This molecule is called POLYETHENE (i.e. polythene), and the process that made it is called POLYMERISATION

6. 26/04/2017
C2.3 Molecular Structure

7. Uses of addition polymers
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Poly(ethene)
Poly(propene)
Poly(styrene)
Poly(chloroethene), PVC

8. Words – high, low, strong, weak, stretched, rigid
Structure of Plastics
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1) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ________ easily
2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____.
Words – high, low, strong, weak, stretched, rigid

9. Forces between molecules
26/04/2017
As we’ve already said, longer molecules have stronger forces of attraction between them. This tends to lead to longer chain plastics being:
Stronger
Stiffer
Harder
More difficult to melt (i.e. higher melting point)

10. Modifying Plastics Polymers can be modified in a number of ways:
26/04/2017
Polymers can be modified in a number of ways:
Increasing the chain length
...making it stronger
2) Crosslinking
...making it harder
3) Plasticizing
...making it softer and more flexible
4) Packing more closely (a crystalline polymer)
...making it stronger and more dense

11. What makes polymer properties?

12. What makes polymer properties?
Method
How properties change
Making chains longer
Stronger
Higher melting point
Harder
Less flexible
Adding cross-links
Adding plasticisers
Softer
More flexible
Lower melting point
Increasing crystallinity by lining up polymer molecules
Denser

13. 26/04/2017
C2.4 Nanotechnology

14. Nanotechnology
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Definition:
The use/control of structures called nanoparticles which are VERY small.

15. How nanoparticles are formed
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Nanoparticles can be formed by a number of methods:
They can occur naturally in sea spray
They can also be formed during combustion
Or they can be formed by grinding down materials

16. Two examples of nanotechnology
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The “Nano Carbon Pro” tennis racket uses nanoparticles to increase its strength.
Silver nanoparticles can be used to give fibres antibacterial properties – look at what they do to e-coli bacteria:
Normal e-coli
E-coli affected by silver nanoparticles

17. Nanoscience and health
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Nanoparticles are obviously very small and, as we have said, have a large surface area to volume ratio. This makes them useful but can also make them dangerous. Nanoparticles could easily pass through a cell membrane:
I’m going to die…
How do these health concerns affect the development of nanotechnology?

22. Properties Negative effects How to reduce effects 6 marks 8 minutes to answer.

23. Answer