Alkenes

What is Alkenes?

Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains Alkenes. Chemistry links what you can see in the lab to the particles and bonds behind it, so each topic here shows that link in a model.

Check that you can explain Alkenes in your own words and give one example from everyday life. If you can do that, you have understood the core idea.

Understanding Alkenes helps you explain why substances behave as they do, from cleaning products and food to medicines.

Alkenes in detail

Alkenes are unsaturated hydrocarbons with at least one carbon–carbon double bond and the general formula CₙH₂ₙ. The first are ethene (C₂H₄) and propene (C₃H₆). The double bond makes them more reactive than alkanes.

They undergo addition reactions: with hydrogen to form alkanes, with halogens such as bromine to form dibromo compounds, and with steam to form alcohols. Bromine water turns from orange to colourless in the presence of an alkene, which is the test for unsaturation. Alkenes are the building blocks of polymers.

How the interactive helps you understand Alkenes

Click a card to flip it and reveal the answer, then move on to the next one.

Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Alkenes.

Real-life uses and examples

• Explain Alkenes in an exam by linking the particles involved to what you observe.
• Use Alkenes to explain what happens in a lab experiment and why.
• Link Alkenes to everyday products such as cleaning agents, food and medicines.

Common mistakes to avoid

• Mixing up the names of substances or ions when you describe Alkenes.
• Describing what happens without explaining the particles or bonds involved.
• Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.