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Bromine water

You can use bromine water, which is an orange solution, to distinguish between alkanes and alkenes.

Addition reactions with different reactants

Alkenes can react with different types of chemicals during addition reactions.

Alkene + hydrogen → alkane

This process is called hydrogenation, and it requires a catalyst.

For example:

propene + hydrogen → propane

Alkene + water (steam) → alcohol

This process is called hydration. It requires a temperature of approximately 300°C and a catalyst.

For example:

ethene + water (steam) → alcohol

Chlorine, bromine or iodine can be added to an alkene. These reactions are usually spontaneous. Here are some examples (you would not be expected to name the product of any of these reactions but you would be expected to draw it or write its formula)

ethene + chlorine → 1,2-dichloroethane

ethane + iodine →1,2-diiodoethane