21/04/2321/04/23

C2 Material ChoicesC2 Material ChoicesThis PowerPoint supports the C2 topic from the

2011 OCR 21st Century course

21/04/23Hydrocarbons and crude oil

Incre

asin

g le

ng

th

Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:

Ethane

C C

HH

H

HH

H

Butane

C C

HH H

HH

H C C H

H

HH

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.

Words – boiling, fractions, plastics, fuels

21/04/23Fractional distillation

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

21/04/23Forces between molecules

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.

21/04/23Polymers

C CHH

HH

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

21/04/23C2.3 Molecular Structure

21/04/23Uses of addition polymers

Poly(ethene) Poly(propene)

Poly(chloroethene), PVC

Poly(styrene)

21/04/23Structure of Plastics

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

21/04/23Forces between molecules

As we’ve already said, longer molecules have stronger forces of attraction between them. This tends to lead to longer chain plastics being:

1) Stronger

2) Stiffer

3) Harder

4) More difficult to melt (i.e. higher melting point)

21/04/23Modifying Plastics

Polymers can be modified in a number of ways:

1) 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

What makes polymer What makes polymer properties?properties?

What makes polymer What makes polymer properties?properties?Method How properties change

Making chains longer

•Stronger •Higher melting point•Harder•Less flexible

Adding cross-links •Harder•Stronger•Less flexible•Higher melting point

Adding plasticisers •Softer•More flexible•Lower melting point

Increasing crystallinity by lining up polymer molecules

•Stronger•Denser•Less flexible•Higher melting point

21/04/23C2.4 Nanotechnology

21/04/23Nanotechnology

The use/control of structures called nanoparticles which are VERY small.

Definition:

21/04/23How nanoparticles are formed

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

21/04/23Two examples of nanotechnology

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

21/04/23Nanoscience and health

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:

How do these health concerns affect the development of nanotechnology?

I’m going to die…

Properties Negative effectsHow to reduce effects6 marks8 minutes to answer.

Answer Answer