OCR 21st Century Science, Chemistry - C2

Materials that are obtained by living things:

• cotton - plant
• paper - wood
• silk - silk worm
• wool - sheep

Strength of polymers - the bonds between the atoms in a molecule are strong which don't break when a molecule is pulled apart. The bonds between  molecules are weak which break easily.

The right materials - In order to choose the right materials the manufactures must know the materials properties like hard or soft, stiff or flexible and strong or weak.

Properties of materials - The properties of different materials depend on how its made like the visible weave of a fabric, the microscopic shape and texture of the fibres and the invisible molecules that make up the polymer.

Plastics can bring benefits to people by meeting their needs. These include:

• Physical needs for shelter, warmth and transport
• Bodily needs for food, water, hygiene and health care
• Social and emotional needs for human contact, leisure and entertainment.
• Needs of the mind to stimulate thinking and creativity.
• Polythene bags – help people to store and carry food.
• Polypropylene – new legs made for people.
• PVC – the world’s first inflatable church made form PVC.
• PET – Polyester used to make soft drinks bottles and other food containers.
• Polyester – used to make hulls and sails.
• Polycarbonate – Manchester city stadium is made from polycarbonate glass.
• Kevlar – helmets for soldiers.
• Neoprene – used to make wet suit which offers warmth and protection.
• Natural rubber (latex) – gloves made for doctors and other health workers for protection and to prevent infection.

Silk and wool - Silk has smooth, straight fibres that slide across each other whereas wool has rough which are covered in scales. Wool fibres tend to cling together in the thread making the tread cling together.

Size of atom - 1 nanometre equals to 1000 000 000 times smaller than a metre.

Crude Oil - When taken out, crude oil is a thick, black, sticky liquid which contains hydrocarbons. Different hydrocarbons have different melting points because their moleculer chains are different lengths and can be seperated by fractional distillation.

Life cycle of a product - Manufacture: resources and energy needed to make the product, Use: energy needed to use the product and disposal: energy needed to dispose of the product.