C2 - Revision Summary

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Iron is a chemical element -its made up of only iron atoms.

A material that we use that comes from plants is wood and paper which both comes from trees. A material that we use that is from animals is leather which comes from cows.

The advantage of synthetic rubber over natural rubber is that it is made in factories where you can control the properties, making it suitable for different purposes, e.g wet suits.

Strength is how good a material is at resisting a force. Stiffness is how good a material is at not bending when a force is applied to it.

The hardest material found in nature is diamond.

Density is the mass per unit volume.

Plastics- can be fairly hard,strong and stiff, some are mouldable. Rubber- strong but soft and flexible, mouldable. Nylon- soft and flexible, good tensile strength.

Crude oil contains a mixture of hydrocarbons.

Covalent bonds- between the carbons and hydrogens within each hydrocarbon molecule. Inter molecular forces- attraction between different hydrocarbon molecules in the mixture.

Big hydrocarbon molecules have higher boiling points than smaller ones because the inter molecular forces of attraction are much stronger between big molecules than smaller ones.Therefore more energy is needed for them to break out of a liquid and form a gas

When crude oil is refined it is separated into groups with different boiling points.

Some useful products of crude oil are: petrol, diesel, kerosene, lubricating oil and bitumen.

Most of the hydrocarbons is crude oil are used to produce fuels.

During polymerisation small molecules called monomers join together(polymerise) to make a very long molecule called polymers.

Window frames are no longer made from wood but use a polymer known as PVC as it is weather-resistant, durable and strong, making window frames more secure and means that frames do not need painting every few years.

Polymer chains that are packed closely together have a high density. If the chains are spread out then it has a low density.

A polymer that is easily stretched and has a low melting point has weak forces holding them together.

To make a polymer stiffer and stronger you would add cross links.

Plasticizers work by getting inbetween the polymer chains and reducing the forces between them.This makes the polymer softer and easier to shape.

The properties of a crystalline polymer are straight chains with no branches so the chains can fit close together. Making the polymers have a high density and boiling point and stronger.

Nanotechnology is the branch of technology dealing with the making and use of nanoparticles.

Nano particles are added to some sports equipment to make the plastic much stronger and more durable and they don't add weight. e.g tennis rackets. Silver nanoparticles are added to polymer fibres used to make surgical masks and wound dressings. This gives the fibres antibacterial properties.