Cracking Hydrocarbons And Polymers (5) Flashcards
Long hydrocarbons have _________ boiling points and are quite __________
High
Viscous
Shorter hydrocarbons have lower boiling points, are much more ________ and are more ________ in colour
Thin
Pale
Demand for _________-chain hydrocarbons like octane, which is used in petrol, is much higher than that for _________-chain hydrocarbons. So to meet this demand ________-chain hydrocarbons are split into _________-chain hydrocarbons using ____________
Long-chain
Long-chain
Short-chain
Cracking
What is cracking
A form of thermal decomposition which just means breaking molecules down into a simpler molecules by heating them
Cracking also produces ______________ which are used to make _________________
Alkenes
Polymers
Name a condition for a catalyst
Heat
Name 2 catalysts for cracking
Silica
Alumina
Explain a cracking experiment
Heat the paraffin. After a few seconds, move the bunsen burner to heat the catalyst. Alternate between the 2 until the paraffin vaporises andthe catalyst glows red. The heated paraffin vapour cracks as is passes over the heated catalyst
Small alkanes collects at the end of the boiling tube, while alkenes travel down the delivery tube
The alkenes are then collected through water using a gas jar
Plastics are formed when lots of small molecules called ____________ join together to make a ______________
Monomers
Polymer
What are the 2 basic types of polymer
Addition
Condensation
Addition polymers are made under ________ pressure
High pressure
Are monomers that make up addition polymers alkanes or alkenes
Alkenes
Explain the process of making addition polymers
Under high pressure and with a catalyst, many small molecules will open up the double bonds of the alkenes and polymerise (join hands) to form very long saturated chains
Addition polymerisation reactions can be written as an equation using _____________ units
Repeating
In the exam, you could be asked to draw the repeat unit of a polymer. What do you do.
Just find the section of the polymer that’s repeated, draw it and put in brackets with an n
How do you find the monomer used to form an addition polymer
Take the repeat unit and add a double bond
What is the biggest difference between addition polymerisation and condensation polymerisation
Condensation polymerisation usually involves 2 different types of monomer
How does condensation polymerisation work
2 monomers react together and bonds form between them, making polymer chains. For each new bond that forms, a small molecule (e.g water) is lost
Give an example of a condensation polymer
Nylon
Name 2 different types of polymers
Poly(ethene)
Poly(propene)
What is poly(ethene)
A light, stretchable polymer
What is poly(propene)
A very tough polymer, but relatively flexible and resistant to heat
What is poly(ethene) useful for
Ideal for packaging
E.g. plastic bags, bottles and other containers
What is poly(propene) useful for
It’s used to make things such as: Kettles, food containers and carpets
