C4 Flashcards
What are polymers?
Long chain molecules formed when monomers are joined together
What is usually required to make polymers synthetically?
High pressure and a catalyst
How does addition polymerisation work?
Where many alkenes open their C=C bond and join together, forming a polymer
How does condensation polymerisation work?
When two different monomers react and form a bond between them, while releasing a by-product (normally water)
How do you show the repeating unit of a polymer?
You take the monomer, turn the double bond into a single and draw bonds either side of the carbons, then put a pair of brackets and put an ‘n’ on the outside
What are the 2 different types of condensation polymers?
Polyester and polyamides
When are polyesters formed?
When dicarboxylic acid monomers and diol monomers react, forming an ester link (O=C-O), and a by product of water
When are polyamides formed?
When dicarboxylic acid and diamine monomers react, forming an amide link (O=C-N-H), and a by product of water
Why is water formed in condensation polymerisation?
Because 2 hydrogen atoms and 1 oxygen atom are released in order for a 1 bond to be formed
How do you find the formulas of the monomers in a condensation polymer from it’s repeating unit?
1) Find the ester or amide link, and break it down the middle
2) Add an H or an OH to both ends of both molecules
What does an amide link look like?
O=C-N-H
What does an ester link look like?
O=C-O
Give 3 examples of natural polymers
DNA, Carbohydrates, Proteins
How are polymers held together?
The atoms in each chain are bonded via strong covalent bonds, but the chains are held together by weaker intermolecular forces
What are low density polymers?
Polymers that are made with lots of space in between chains, so are flexible but have relatively weak intermolecular forces
What are high density polymers?
Polymers that are packed closely together, so are stiff and have stronger intermolecular forces
What are crosslinks and what do they do?
They are covalent or ionic links between polymer chains which make it stiffer, stronger, harder and have a high MP
What is the structure and properties of giant covalent structures?
Atoms bonded by strong covalent bonds
High melting and boiling points
Do not conduct (except graphite and graphene)
What is the structure and properties of diamond?
- Made of carbon
- Each carbon covalently bonded to 4 other carbons
- Giant covalent structure
- High MP and BP
- Does not conduct
- Shiny and lustrous
What is the structure and properties of graphite?
- Made of carbon
- Each carbon covalently bonded to 3 other carbons
- Structure in layers, which are held together weakly
- High MP and BP
- Conducts
- Black but still kind of shiny
What does graphite conduct and diamond not?
Because in diamond, each carbon atom is covalently bonded to 4 other carbons, therefore there is no free electrons, whereas in graphite each carbon is only covalently bonded to 3 other carbons, so there is free electrons
What is graphene and what are its properties?
- A single sheet of graphite
- Very strong
- Transparent
- Light
- Great conductor
What are ceramics and what are their properties?
Materials made by baking clay, which are stiff but brittle
What are composites and what are their properties?
One material embedded in another, which takes on the properties of the materials it’s made from (e.g. concrete mixed with steel makes a harder, stronger wall)
What are alloys and what are their properties?
A mixture of a metal and at least one other element, which takes on the properties of the elements it’s made from
What is a redox reaction?
A reaction involving both oxidisation and reduction
What is the chemical equation for the corrosion of iron (rusting)?
Iron + Oxygen + Water > Hydrated Iron Oxide
What are the 2 main methods of preventing corrosion?
1) Creating a barrier between the metal and the water and oxygen
2) The sacrificial method, in which you attach a more reactive metal, which will react with the water and oxygen instead of the metal you are protecting
State 3 examples of the barrier method is preventing corrosion
- Painting
- Coating in plastic
- Greasing/oiling
Give an example of the sacrificial method is preventing corrosion
Attaching large magnesium blocks on steel ships
Where in recycling do you require energy?
In collection, sorting and preprocessing
What are life-cycle assessments?
Where you look at the life of a product and the different stages, working out the environmental impact
What are the main stages in life-cycle assessments you must consider?
- Choice of material
- Manufacture
- Shipping
- Product use
- Disposal
What is 1nm?
1x10^-9m
What are fullerenes?
- Nanoparticles of carbon
- Arranged in rings similar to graphite
- Have delocalised electrons, so can conduct
- High tensile strength
What are the properties of nano-particles
Nanoparticles are so small that they have different properties than the same substance in normal-sized pieces- they have an incredibly high surface area to volume ratio
Give 3 examples of uses of nanoparticles
- Sun creams/deodorants
- Can cause drugs to be absorbed easier, and could deliver drugs to the right areas, faster
- Add to materials to make them stronger while adding little mass
What are some of the concerns of nanoparticles?
- They are so small they are able to get into cells deep within the body, and they could react in unknown ways
- They are generally new tech, so have not been tested a lot for the possible hidden risks
