Quick questions on Alkenes and addition reactions explained: O-Level Chemistry

The alkenes are a homologous series of hydrocarbons that contain a carbon-to-carbon double bond ($\text{C}=\text{C}$). Because the double bond means the carbons are not bonded to the maximum number of hydrogen atoms, the alkenes are unsaturated. Their general formula is:

In an addition reaction, the double bond opens and atoms add across it, so two molecules become one with no atoms lost. Key examples:

The test that distinguishes an alkene from an alkane uses bromine water (aqueous bromine), which is orange-brown:

Many alkene molecules can join together to form a very long chain in addition polymerisation. The small starting molecules are called monomers (such as ethene), and the long molecule formed is the polymer (such as poly(ethene)). In the reaction, the double bond of each monomer opens and the molecules join end to end into a single chain, with no small molecule lost. Poly(ethene) is the familiar plastic used for bags and bottles.

State the general formula of the alkenes and the name of the bond that makes them unsaturated. [1 mark]

Describe the result of adding bromine water to an alkene and to an alkane. [2 marks]

Name the small molecule and the large molecule in addition polymerisation, and state what happens to the double bond. [2 marks]