'3.6 and 3.7 I can recall the general formula and displayed formulae of alkenes

4. What is the general formula for alkenes?

CNH2N

5. Describe and explain the trend in boiling point

As the boiling point increases there are stronger inter molecular forces that need more energy to be broken.

6. Explain why there is no such compound as methene

There is no such compound as methene because to be classed as an alkene the compound needs to have a double bond when is not possible in methene because it only has one carbon.

7. How do you quickly identify from the displayed formula that the hydrocarbon is unsaturated?

This is done by looking for a carbon double bond which indicates it is unsaturated.