C1d

Question 1

What are the two elements chemically combined in a hydrocarbon?

Answer 1

Carbon and hydrogen.

Question 2

How do you recognise a hydrocarbon from its molecular or displayed formula?

Answer 2

There will only be C’s and H’s and no other letters.

Question 3

What is a hydrocarbon?

Answer 3

A compound formed between carbon atoms and hydrogen atoms only.

Question 4

What is a saturated compound?

Answer 4

One which contain only single covalent bonds between carbon atoms.

Question 5

What is an unsaturated compound?

Answer 5

One which contains at least one double covalent bond between carbon atoms.

Question 6

What are alkanes?

Answer 6

Hydrocarbons which contain single covalent bonds only.

Question 7

How can you tell that a displayed formula is an alkane?

Answer 7

There will be single bonds between carbon atoms only and all alkanes have the formula CnH2n+2.

Question 8

What are alkenes?

Answer 8

Hydrocarbons which contain a double covalent bond between carbon atoms.

Question 9

What do double bonds involve?

Answer 9

Two shared pairs of electrons.

Question 10

How can you tell that a displayed formula is a alkene?

Answer 10

All alkenes have at least one double bond.

Alkenes only containing one double bond have the formula CnH2n.

Question 11

Explain the reaction between bromine and alkenes.

Answer 11

Bromine water is a bright orange solution that contains bromine, Br2.
It’s really reactive - if there are any double bonds around, they’ll spring open and react with the bromine. When this happens the orange colour disappears from the solution - the bromine water is decolourised.
You can use this to test whether what you’ve got is an alkene or not. You take a sample of your hydrocarbon, mix it with bromine water, and shake.
If it’s a saturated compound, like an alkane, no reaction will happen and it’ll stay bright orange.
If it’s an alkene an addition reaction will take place. The bromine will add to the double bond, making a colourless dibromo compound - so the bromine water is decolourised.

Question 12

How do you deduce the name of an addition polymer given the name of the monomer and vice versa?

Answer 12

The name of the monomer comes from the type of monomer it’s made from - you just stick the word ‘poly’ in front of it. So propene becomes Polypropene.

Question 13

How do you recognise the displayed formula of a polymer?

Answer 13

Double bonds will open up and go through the brackets.

Question 14

How do you draw the displayed formula of an addition polymer given the displayed formula of its monomer?

Answer 14

Join the carbons together in a row with no double bonds between them, stick a pair of brackets around the repeating bit, and put an ‘n’ after it to show that there are lots of monomers.

Question 15

How do you draw the displayed formula of a monomer given the displayed formula of its addition polymer?

Answer 15

Draw out the repeating bit of the polymer, get rid of the two bonds going out through the brackets and put a double bond between the carbons.

Question 16

When are polymers formed?

Answer 16

When lots of small molecules called monomers join together. This reaction is called polymerisation - and it needs a high pressure and a catalyst.

Question 17

What is addition polymerisation?

Answer 17

Addition polymers are made from unsaturated monomers. The monomers that make up addition polymers have a double covalent bond. Molecules with at least one double covalent bond between carbon atoms are called unsaturated compounds. Molecules with no double bond between carbon atoms are saturated compounds. Lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains. This is called addition polymerisation.