Welcome back to Berry Berry Easy. We are pleased to present you with the Part 4 of the SPM Form 5 Chemistry notes on Carbon Compound. For those who have learnt about “alkanes” in Part 2 and “alkenes” in Part 3, now you can compare between the two groups. You’ll be exposed to the similarities and differences in the properties of the two homologous groups and also isomerism in both groups. Be sure to check out the previous three parts if you have not done so.
SPM Form 5 – Terminology and Concepts: Carbon Compounds
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. |
2. Isomerism
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 |
Isomerism in alkenes
| 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 |
As mentioned in the first part of the notes in this series, this will be a rather long set of notes. So, remember to drop by Berry Berry Easy to get updates for the notes. 
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