C4 Flashcards
What are plastics made up of?
Polymers
What are polymers?
Molecules formed when monomers are joined together.
To make polymers, high pressure and a catalyst are required
What are addition polymers made up of?
Made up of monomers which have a carbon-carbon double bond functional group.
What is condensation polymerisation?
2 different monomers with different functional groups which react together, forming bonds.
What are polymers held together by?
In polymers, all the atoms are held together by strong covalent bonds.
There are intermolecular forces between the chains
What are the properties of Low density polyethene?
Lots of space between polymer chains, so forces are weak
-This makes it flexible so it is used for plastic bags
What are the properties of High density polyethene?
Chains have strong forces of attraction, which makes it stronger and is used for watertanks.
What do polymers which only contain intermolecular forces have?
Contain individual tangled chains
- can slide over each other
- the forces between the chains can be overcome, so the polymers can be melted.
What are the properties of polymers with cross-links?
The chains are held together strongly.
- polymers don’t soften when heated
- strong, hard and stiff.
What are giant covalent structures?
Atoms bonded by strong covalent bonds
High melting and boiling points
Do not conduct
What is diamons?
Forms 4, strong covalent bonds
- very hard
- High melting point
- Doesn’t conduct as it has no free electrons
What is graphite?
Only forms 33 covallent bonds, creating sheets of carbon atoms.
- layers are held together by weak intermolecular forces so can be rubbed off each other.
- high melting point as covalent bonds are hard to break
- graphite can conduct as there are free eletrons
What is graphene?
A single sheet of graphine
What is an example of ionic bonding?
NaCl
What is an example of simple molecular bonding?
CO2
What is an example of metallic bonding?
Iron
What is an example of a polymer?
Polyethene
What is an example of giant covalent structure?
Diamond
What are the different bulk properties of materials?
- Melting point
- Strength
- Stiffness
- Hardness
- Brittleness
- Ease of reshaping
- Conductivity
What are the properties of ceramics?
Stiff but brittle material
What are composites?
Made of different materials.
What are alloys?
A mixture of metals and other elements
What are polymers suited to?
Some are flexible, so can be moulded into any shape
Others are strong so can be used for objects like lunchboxes.
What are ceramics suited to?
Windows as they are strong and hard wearing
What are metals suited to?
Suited to corrosion materials as they are strong.
What is a redox reaction?
Where a metal loses electrons when corroding.
What is required for Iron to corrode?
Oxygen and water
What methods are there to prevent corrosion?
Creating barriers between metal and water and oxygen:
-Painting / coating with plastic
Sacrificial method:
-galvanising iron with zinc. The zinc may corrode or be scratched but the iron will not
What is the difficulty of extracting raw materials?
Requires energy
- however products can be reused
- the energy comes from burning fossil fuels
How are plastic water bottles recycled?
Made from polymer PET.
- plastic waste is sorted to seperate PET objects from other plastic materials
- PET is shredded and cleaned, then melted to make new products
- recycling PET is viable as it uses less materials than creating new PET.
What are the difficulties with recycling?
Recycling requires energy and resources to collect materials, sort them.
What does a life cycle assessment consist of?
1) Choice of material
2) Manufacture
3) Use of product
4) Disposal
What does each stage of the life cycle assessment take in to account?
- How much damage it will do to the environment
- How much energy is required
- Is it biodegradable?
What is the size (diameter) of a nanoparticle?
0.000000001m
Why do nanoparticles have a large surface:volume ratio?
A higher proportion of the atoms are at the surface are able to react with more substances.
What are fullerences?
Nanoparticles of carbon
Arranged in rings similar to graphite
-have delocalised electrons, so can conduct
-high tensile strength
How can nanopartiicles modify the properties of metals?
- High surface:volume ratio so make good catalysts
- can cause drugs to be absorbed easier
- new coatings made with fullerences
- conduct so can be used in circuits
What do people worry about the effects of nanoparticles on health?-
People believe they are small and may have unexpected side affects
- benefits have to be weighed up against the risks
- people believe products containing nanoprticles have been made availble before tested on humans.
