Products from Crude Oil Flashcards
What is cracking?
Large hydrocarbons cracked during thermal decomposition and split to form smaller hydrocarbons
Describe the cracking process
A heavy fraction of crude oil is vapourised and is passed over a hot catalyst and heated to a very high temperature. The hydorcarbons are cracked in thermal decomposition and split to form smaller hydrocarbons
Are alkenes saturated or unsaturated?
What does this mean?
Unsaturated, they contain at least one double bond
What is the general formula for alkenes?
CnH2n
Give a chemical test which shows the difference between alkane and alkene
Test: bromine water
Result of test: alkene - changes from orange/brown to colourless, water reacts with double bond
alkane - bromine water stays orange/brown
How can you make ethanol?
C2H4 + H2O ⇔ C2H5OH
ethene + steam catalyst ethanol
- High temperatures and pressure
- Phosphoric acid catalyst
- Continuous process
Definition of a monomer
A small molecule with a c=c that can combine with other similar molecules to form a long molecule known as a polymer
Definition of a polymer
A substance consisting of very long molecules made of smaller molecules called monomers
Definition of polymerisation
The process in which monomers join together to form a large polymer molecule
Describe the process of addition polymerisation
- The monomers are put under pressure and high temperature
- The double bonds break open
- Millions of monomer molecules joining together by single bonds
- Form one long molecule called a polymer
What is the general equation for making polymers?
Thermosoftening plastics
- Structure and bonding
- Upon heating
- Properties
- Examples
- Individual tangled polymer chains with weak intermolecular forces (relatively easy to separate)
- Becomes soft and runny. Heat overcomes the WIFs and the chains slide over each other. Once cooled it can be hardened into a new shape
- Flexible (weak forces between chains)
→ High tensile strength
→ Low melting points
- Poly(ethene), Poly(propene), Poly(chloroethene)
Thermosetting plastics
- Structure and bonding
- Upon heating
- Properties
- Examples
- Polymer chains with strong cross links (covalent bonds)
- When first made, strong chemical bonds called cross links form between the chains. The solid sets into shape and stays heart even when heated - do not melt
- Heat resistant (break down, don’t melt, strong cross links)
→ Rigid - break rather than bend
→ High melting points
- Melamine - plates; Bakelite - saucepan handles
Describe low density poly(ethene)
- Formed under high temperatures and high pressures
- Branches form from the chains and cannot pack closely together
→ weak intermolecular forces
- Flexible, used in plastic bags and gloves
Describe high density poly(ethene)
- Formed under low termperatures, slight pressures and with a catalyst
- Chains pack much closer together
→ stong intermolecular forces
- Rigid but still light, so used in plastic bottles and containers
