Carbon Chemistry - Polymerisation Flashcards
Why alkenes not used as fuels?
Because the double bond means that they undergo incomplete combustion.
Why are alkenes used to make polymers?
Because their double bond can be broken, allowing many alkenes to be joined together to make polymers.
What does polymerisation require? (3)
- High temperatures
- High pressures
- Presence of a catalyst
What state are polymers are room temperature?
Solid because they are long-chained hydrocarbons
Why do the molecules form strong chemically resistant fibres?
Because the carbon chain length is bonded with strong covalent bonds.
What to remember when drawing the formulae of polymers
- Brackets
- THE N OUTSIDE THE BRACKET
- NAMED AFTER ALKENE
What is a monomer?
A small molecule that can be combined with other molecules to make long chains.
Briefly outline the process of cracking
Alkenes are unsaturated hydrocarbons meaning the double bond can be broken, allowing many alkenes to join together. Each alkene molecule is called a monomer. In the presence of high temperature, high pressure and a catalyst, the bonds are broken and neighbouring alkenes are joined together to form polymers which are very long-chained hydrocarbons.
What is polypropene used for?
-Packaging, labelling, textiles (ROPES, THERMAL UNDERWEAR and carpets), stationery, reusable containers of various types, bottle caps, DRINKING STRAWS, yoghurt containers, appliances, car parts, LABORATORY EQUIPMENT, loudspeakers, margarine tubs and polymer bank notes.
Why is polypropene used to make fabrics, food containers etc
- low chemical reactivity (with air, water and living organisms)
- excellent resistance to concentrated acids, alcohols, bases and mineral oils
- INSOLUBLE IN WATER
- can be moulded or extruded into a wide range of shapes with moderate heating
- thermal insulator
- floats (less dense than water)
- recyclable
- excellent resistance to stress and is highly resistant to cracking.
- DOES NOT PROMOTE GROWTH OF BACTERIA
Uses of polyethene
HDPE: low pressure and heat and catalyst, long linear straight chains.
-pipes, margarine tubs, rubbish bins, plastic bottles
LDPE: high pressure and heat and catalyst, chains with branches
-gladwrap and soft tubing
Why are polymers (polythene and polypropene) chemically unreactive?
because all valence electrons are used in single covalent bonds.
Describe polymers
Macromolecule and a hydrocarbon made up of repeated monomers of alkenes.
