1. Comparing (Similarities and Differences) Properties of Alkanes and Alkenes
| Physical Properties | Alkanes | Alkenes |
| Physical state | Physical state changes from gas to liquid when going down the series. | Same with alkanes. |
| Electrical conductivity. | Do not conduct electricity at any state. | Same with alkanes. |
| Boiling points and melting points | Low boiling points and melting points (number of carbon atoms per molecule increases). | Same with alkanes. |
| Density | Low densities (number of carbon atom per molecule increases). | Same with alkanes. |
| Solubility in water | Insoluble in water (soluble in organic solvent) | Same with alkanes. |
| Chemical Properties | Alkanes (Substitution reaction) | Alkenes (Addition reaction) |
| Reactivity | Unreactive | Reactive |
| Combustion | Burn in air and produce yellow sooty flame. | Burn in air and produce yellow and sootier flame compare to alkanes. |
| Reaction with bromine solution | No reaction. | Decolourise brown bromine solution. |
| Reaction with acidified potassium manganate(VII) solution | No reaction. | Decolourise purple acidified potassium manganate(VII) solution. |
Isomerism – phenomenon that two or more molecules are found to have the same molecular formula but different structural formulae.
Isomerism in alkanes
| Molecular formula | Number of isomers | Structure name |
| CH4 | - (no isomer) | Methane |
| C2H6 | - (no isomer) | Ethane |
| C3H8 | - (no isomer) | Propane |
| C4H10 | 2 | Butane2-methylpropane |
| C5H12 | 3 | Pentane2-methylbutane2,2-dimethylpropane |
| Molecular formula | Number of isomers | Structure name |
| C2H4 | - (no isomer) | Ethene |
| C3H6 | - (no isomer) | Propene |
| C4H8 | 3 | But-1-eneBut-2-ene2-methylpropene |
| C5H10 | 5 | Pent-1-enePent-2-ene2-methylbut-1-ene
3-methylbut-1-ene 2-methylbut-2-ene |
