C2 Revision Notes

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C2 –

How do we measure the properties

of materials and why are the results useful? -

Solid materials can

differ with respect to properties such as melting point, strength (in

tension or compression), stiffness, hardness and density.

Properties relate

to the uses of materials such as plastics, rubbers and fibres

The effectiveness

and durability of a product relates to the materials used to make it.

The properties of

materials such as plastics, rubbers and fibres relate to suitability of

these materials for particular purposes.

Why is crude oil important as a

source of new materials such as plastics and fibres? –

The materials we

use are chemicals or mixtures of chemicals, and include metals, ceramics

and polymers.

Materials can be

obtained or made from living things, such as cotton, paper, silk and wool.

There are synthetic

materials that are alternatives to materials from living things.

Raw materials from

the Earth’s crust can be used to make synthetic materials.

Know

representations of rearrangements of atoms during a chemical reaction.

In a chemical

reaction the numbers of atoms of each element must be the same in the

products as in the reactants.

Crude oil consists

mainly of hydrocarbons, which are chain molecules of varying lengths made

from carbon and hydrogen atoms only.

Only a small

percentage of crude oil is used for chemical synthesis and that most is

used as fuels.

The petrochemical

industry refines crude oil by fractional distillation; hydrocarbons are

separated into fractions of different boiling points, to produce fuels,

lubricants and the raw materials for chemical synthesis.

Relate the size of

the forces between hydrocarbon molecules to the size of the molecules.

Relate the strength

of the forces between hydrocarbon molecules in crude oil to the amount of

energy needed for them to break out of a liquid and form a gas, and to the

temperature at which the liquid boils.

Some small molecules

called monomers can join together to make very long molecules called

polymers, and that the process is called polymerisation.

Know two examples

of materials that, because of their superior properties, have replaced

materials used in the past.

Why does it help to know about

the molecular structure of materials such as plastics and fibres?

It is possible to produce a wide range of

different polymers with properties that make them each suited to a

particular use.

The properties of

polymers depend on how their molecules are arranged and held together.

Relate the strength

of the forces between the molecules in a polymer to the amount of energy

needed to separate them from each other, and therefore to the strength,

stiffness, hardness and melting point of the solid.

Modifications in

polymers produce changes to their properties to include modifications such

as:

a) increased chain

length

b) cross-linking

c) the use of

plasticizers

d) increased

crystallinity

What is nanotechnology and why is

it important? -

Nanotechnology

involves structures that are about the same size as some molecules.

Nanotechnology is

the use and control of structures that are very small (1 to 100 nanometres

in size).

Nanoparticles can

occur naturally (for example in sea spray), by accident (for example as

the smallest particulates from combustion of fuels), and by design.

Nanoparticles of a

material show different properties compared to larger particles of the

same material, and that one of the reasons for this is the much larger

surface area of the nanoparticles compared to their volume.

Nanoparticles can

be used to modify the properties of materials, and give examples

including:

a) the use of

silver nanoparticles to give fibres antibacterial properties,

b) adding

nanoparticles to plastics for sports equipment to make them stronger.

Some nanoparticles

may have harmful effects on health, and that there is concern that

products with nanoparticles are being introduced before these effects have

been fully investigated.