# Ethene is a member of the alkenes homologous series. Describe the structure of ethene and explain why alkenes, unlike alkanes, can undergo addition reactions to form polymers.

> AQA A-Level Chemistry (7405) — 3.3.4 Alkenes · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Ethene contains a carbon-carbon double bond
2. Ethene / alkenes are unsaturated
3. The double bond can open / break to allow other atoms / molecules to add on
4. Many alkene monomers join together (to form a polymer)
5. Alkanes are saturated / only have single bonds so cannot undergo addition reactions / cannot open a double bond

## Key terms

- [alkenes](https://www.gradenine.co.uk/glossary/alkenes)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/ethene-is-a-member-of-the-a14230e5) · Published by Druglandscape Ltd.