1. 25/03/2017
25/03/2017
C2 Material Choices
OCR 21st Century
W Richards

2. C2.1 Properties of Materials
25/03/2017
Q. For each of the following materials describe what properties the material needs to have and why…

3. Properties of materials
25/03/2017
Plastic (polythene)
Light
Flexible
Easily moulded

4. Properties of materials
25/03/2017
Plastic (polystyrene)
Light
Rigid
Good insulation

5. Properties of materials
25/03/2017
Nylon
Light
Tough
Waterproof

6. Properties of materials
25/03/2017
Polyester
Light
Tough
Waterproof

7. Properties of materials
25/03/2017
Unvulcanised rubbers
Low tensile strength
Soft
Flexible

8. Properties of materials
25/03/2017
Vulcanised rubbers
High tensile strength
Hard
Flexible

9. 25/03/2017
C2.2 Crude Oil

10. Using Different Materials
25/03/2017
We use a variety of materials from a variety of different places:
Cotton from plants
Silk from silkworms
Wood and paper from trees
These are all “natural” materials – we can also use synthetic (man-made) ones like plastics – these are often made from materials from within the Earth like crude oil.

11. Chemical formulae
25/03/2017
The chemical formulae of a molecule or compound is simply a way of showing the ratio of atoms in it. For example… Na Cl
= sodium chloride (NaCl) K I
= potassium iodide (KI) O O
= potassium nitrate (KNO3) K N O

12. Chemical formulae Try drawing these: Water H2O Carbon dioxide CO2
25/03/2017
Try drawing these:
Water H2O
Carbon dioxide CO2
Calcium sulphate CaSO4
Magnesium hydroxide Mg(OH)2

13. Simple chemical reactions
25/03/2017 Mg O H Cl
Magnesium oxide +
Hydrochloric acid
Magnesium chloride +
Water
MgO +
2HCl
MgCl2 +
H2O Mg O Cu S
Magnesium +
Copper sulphate
Copper +
Magnesium sulphate Mg +
CuSO4 Cu +
MgSO4
Notice that the number of atoms on each side of the equation is the same!

14. Hydrocarbons and crude oil
25/03/2017
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

15. Fractional distillation
25/03/2017
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

16. Forces between molecules
25/03/2017
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.

17. Polymers
25/03/2017 C H
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

18. 25/03/2017
C2.3 Molecular Structure

19. Uses of addition polymers
25/03/2017
Poly(ethene)
Poly(propene)
Poly(styrene)
Poly(chloroethene), PVC

20. Words – high, low, strong, weak, stretched, rigid
Structure of Plastics
25/03/2017
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

21. Forces between molecules
25/03/2017
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)

22. Modifying Plastics Polymers can be modified in a number of ways:
25/03/2017
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

23. 25/03/2017
C2.4 Nanotechnology

24. Nanotechnology
25/03/2017
Task: To find out what nanotechnology is and what it is used for
What is nanotechnology?
Define the terms nanoparticle and nanocomposite
Gives some examples of its uses
Describe some of the future uses of this technology
Describe some of the ethical concerns over this technology

25. Nanotechnology Definition:
25/03/2017
Definition:
Nanotechnology is a new branch of science that refers to structures built from a few hundred atoms and are 1-100nm big. They show different properties to the same materials in bulk, partly because they also have a large surface area to volume ratio and their properties could lead to new developments in computers, building materials etc.

26. How nanoparticles are formed
25/03/2017
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

27. Two examples of nanotechnology
25/03/2017
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

28. Nanoscience and health
25/03/2017
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?