Here's how it works:

* Dehydration: This means removing water (H₂O) from a molecule.

* Alcohol: An alcohol has a hydroxyl group (-OH) attached to a carbon atom.

* Alkene: An alkene is a hydrocarbon with a carbon-carbon double bond.

During dehydration, the -OH group and a hydrogen atom from an adjacent carbon atom are removed, forming water. The remaining carbon atoms then form a double bond, creating an alkene.

Example:

Ethanol (an alcohol) can be dehydrated to produce ethene (an alkene):

CH₃CH₂OH (ethanol) → CH₂=CH₂ (ethene) + H₂O (water)