Alkenes

Question 1

what are alkenes?

Answer 1

another type of hydrocarbon that contain a C=C double bond between two carbon atoms in their chain

Question 2

what does unsaturated mean?

Answer 2

the alkenes can make more bonds - the double bond (C=C) can open up, allowing the two carbon atoms to bond with other atoms

Question 3

what is the general formula of alkenes?

Answer 3

CnH2n

Question 4

halogens reaction with alkenes

Answer 4

• halogens can react with alkenes to make haloalkanes
• bromine and ethene react together to form dibromoethane
• these are called addition reactions because the C=C double bond is split and a halogen atom is added to each of the carbons
• this reaction happens without UV light because alkenes are more reactive than alkanes

Question 5

bromine water and alkene test

Answer 5

• the reaction between bromine and alkenes is often used as a test for carbon=carbon bonds
• when you shake an alkene with orange bromine water, the solution becomes colourless - this is because the bromine molecules, which are orange, are reacting with the alkene to make a dibromoalkane, which is colourless
• alkanes don’t react with bromine water as they don’t have a double bond - so if you add an alkane to bromine water, the solution will stay orange