Chemistry C2
All topics from OCR 21st century science textbook.
- Created by: ameliaG72
- Created on: 14-05-14 19:46
View mindmap
- C2- Material Choices
- Made from?
- Every material is a chemical or mixture of chemicals
- Examples: ceramic-bricks, wall tiles and plates, metals- vehicles, high-rise buildings and jewellery, polymers- packaging and protective clothing.
- Obtain materials from: living or non-living things
- Examples: cotton, wool, leather and wood
- Every material is a chemical or mixture of chemicals
- Properties
- Key properties are: melting point, tension strength, compression strength, stiffness, hardness and density.
- manufactures want best quality materials for their products.
- Crude Oil
- crude oil is liquid and a mixture of hydrocarbon molecules of different lengths
- Oil companies use fractional distillation to separate the oil
- Fractionating tower does this: oil is heated in furnace- evaporates and moves up the tower, fractions condense at different levels.
- Small molecules have low boiling points and rise to the top of the tower
- Big molecule compounds have high boiling points and condense at the bottom of the tower
- Uses of crude oil: fuels, lubricants and raw materials.
- Polymers
- Are very long molecules, formed when small molecules called monomers join together. This is polymerisation
- 4% of crude oil is used to produce synthetic materials, these do not occur naturally.
- Synthetic materials have replaced natural materials, e.g. ropes are now made using polypropene instead of sisal or using nylon instead of cotton
- Polymer Properties
- Properties depend on how molecules are arranged and held together
- Example: Wax has shorter molecules than polythene. Polythene is stronger, long molecules are tangled and difficult to separate. polythene melts at higher temps as stronger forces of attraction.
- Changing properties: Longer chains- stronger, adding cross links- stronger, harder, less flexible, adding plasticisers- softer, more flexible, increasing crystallinity by lining up polymer molecules- stronger and denser
- Nanotechnology
- is the use and control of tiny structures
- Nanoparticles are same size as some molecules and 1 to 100 nanometres across
- Nanoparticles have diffrent properties to larger molecules mainly due to bigger surface area: volume ratio
- Nano particles occur: naturally in sea spray, by accident when fuels burn, by design e.g. silver in medical dressings and socks or adding to plastics to make them stronger
- May be health risks, some people think they should be studied more before full usage.
- Made from?
Comments
No comments have yet been made