10/04/2310/04/23

C2 Material ChoicesC2 Material Choices

OCR 21st Century

W Richards

10/04/23C2.1 Properties of Materials

Q. For each of the following materials describe what properties the material needs to have and why…

10/04/23Properties of materials

Plastic (polythene)

• Light

• Flexible

• Easily moulded

10/04/23Properties of materials

Plastic (polystyrene)

• Light

• Rigid

• Good insulation

10/04/23Properties of materials

Nylon

• Light

• Tough

• Waterproof

10/04/23Properties of materials

Polyester

• Light

• Tough

• Waterproof

10/04/23Properties of materials

Unvulcanised rubbers

• Low tensile strength

• Soft

• Flexible

10/04/23Properties of materials

Vulcanised rubbers

• High tensile strength

• Hard

• Flexible

10/04/23C2.2 Crude Oil

10/04/23Using Different Materials

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.

10/04/23Chemical formulae

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)

K N

O

O

O

= potassium nitrate (KNO3)

10/04/23Chemical formulae

Try drawing these:

1) Water H2O

2) Carbon dioxide CO2

3) Calcium sulphate CaSO4

4) Magnesium hydroxide Mg(OH)2

10/04/23Simple chemical reactions

Mg OH Cl

Mg ClCl

HH OH Cl

Magnesium

+ Copper sulphate

Mg

O

OCu

O

O S Cu Mg

O

O

O

O S

Magnesium

sulphate

Copper +

H2OMgO +

WaterMagnesium oxide

+ Hydrochloric acid

Magnesium chloride

+

2HCl MgCl2 +

MgSO4Mg + CuSO4 Cu +

Notice that the number of atoms on each side of the equation is the same!

10/04/23Hydrocarbons 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

10/04/23Fractional 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

10/04/23Forces 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.

10/04/23Polymers

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

10/04/23C2.3 Molecular Structure

10/04/23Uses of addition polymers

Poly(ethene) Poly(propene)

Poly(chloroethene), PVC

Poly(styrene)

10/04/23Structure 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

10/04/23Forces 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)

10/04/23Modifying 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

10/04/23C2.4 Nanotechnology

10/04/23Nanotechnology

Task: To find out what nanotechnology is and what it is used for

1) What is nanotechnology?

2) Define the terms nanoparticle and nanocomposite

3) Gives some examples of its uses

4) Describe some of the future uses of this technology

5) Describe some of the ethical concerns over this technology

10/04/23Nanotechnology

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.

Definition:

10/04/23How 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

10/04/23Two 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

10/04/23Nanoscience 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…