11.3

Alkenes

Cambridge IGCSE Chemistry (0620)  · Unit 11: Organic chemistry  · 12 flashcards

Alkenes is topic 11.3 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 11 — Organic chemistry , alongside Formulae, functional groups and nomenclature, Alkanes and Alcohols.  In one line: Hydrocarbons are compounds that contain hydrogen and carbon atoms only.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 12 flashcards — 2 definitions, 5 key concepts and 5 identification cards — covering the precise wording mark schemes reward.  Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Hydrocarbons

Hydrocarbons are compounds that contain hydrogen and carbon atoms only.

Example: Methane (CH₄) and ethane (C₂H₆).

What the Cambridge 0620 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Name Name the fossil fuels: coal, natural gas and petroleum
  2. Name Name methane as the main constituent of natural gas
  3. State State that hydrocarbons are compounds that contain hydrogen and carbon only
  4. State State that petroleum is a mixture of hydrocarbons
  5. Describe Describe the separation of petroleum into useful fractions by fractional distillation
  6. Describe Describe how the properties of fractions obtained from petroleum change from the bottom to the top of the fractionating column, limited to: (a) decreasing chain length (b) higher volatility (c) lower boiling points (d) lower viscosity
  7. Name Name the uses of the fractions as: (a) refinery gas fraction for gas used in heating and cooking (b) gasoline/petrol fraction for fuel used in cars (c) naphtha fraction as a chemical feedstock (d) kerosene/paraffin fraction for jet fuel (e) diesel oil/gas oil fraction for fuel used in diesel engines (f) fuel oil fraction for fuel used in ships and home heating systems (g) lubricating oil fraction for lubricants, waxes and polishes (h) bitumen fraction for making roads
Key Concept Flip

Name the three main fossil fuels.

Answer Flip

The three main fossil fuels are coal, natural gas, and petroleum.

Key Concept Flip

What is the main constituent of natural gas?

Answer Flip

Methane is the main constituent of natural gas. Its chemical formula is CH₄.

Definition Flip

Define hydrocarbons.

Answer Flip

Hydrocarbons are compounds that contain hydrogen and carbon atoms only.

Example: Methane (CH₄) and ethane (C₂H₆).
Definition Flip

What is petroleum?

Answer Flip

Petroleum is a mixture of different hydrocarbons. These hydrocarbons have different chain lengths.

Key Concept Flip

Describe the process of separating petroleum into useful fractions.

Answer Flip

Petroleum is separated by fractional distillation. This process separates hydrocarbons based on their boiling points; lower boiling points rise higher in the column.

Key Concept Flip

How does chain length change from the bottom to the top of a fractionating column?

Answer Flip

From the bottom to the top of the fractionating column, the chain length of the hydrocarbon molecules decreases.

Key Concept Flip

How does volatility change from the bottom to the top of a fractionating column?

Answer Flip

From the bottom to the top of the fractionating column, the volatility of the hydrocarbon fractions increases.

Key Concept Flip

How do boiling points change from the bottom to the top of a fractionating column?

Answer Flip

From the bottom to the top of the fractionating column, the boiling points of the hydrocarbon fractions decrease.

Key Concept Flip

How does viscosity change from the bottom to the top of a fractionating column?

Answer Flip

From the bottom to the top of the fractionating column, the viscosity of the hydrocarbon fractions decreases. Viscosity refers to how easily a liquid flows.

Key Concept Flip

Name the uses of the refinery gas fraction.

Answer Flip

Refinery gas is used as gas for heating and cooking. It's one of the shortest-chain hydrocarbons separated from petroleum.

Key Concept Flip

Name the uses of the gasoline/petrol fraction.

Answer Flip

Gasoline (or petrol) is used as fuel in cars. It's a more volatile and flammable fraction than diesel.

Key Concept Flip

Name the uses of the kerosene/paraffin fraction.

Answer Flip

Kerosene (or paraffin) is primarily used as jet fuel in airplanes. It has a higher boiling point than gasoline.

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11.2 Alkanes 11.4 Alcohols

Key Questions: Alkenes

Define hydrocarbons.

Hydrocarbons are compounds that contain hydrogen and carbon atoms only.

Example: Methane (CH₄) and ethane (C₂H₆).
What is petroleum?

Petroleum is a mixture of different hydrocarbons. These hydrocarbons have different chain lengths.

Tips to avoid common mistakes in Alkenes

More topics in Unit 11 — Organic chemistry

Alkenes sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

11.1 Formulae, functional groups and nomenclature

12 flashcards
11.2 Alkanes

13 flashcards
11.4 Alcohols

11 flashcards
11.5 Carboxylic acids

12 flashcards
11.6 Esters

8 flashcards
11.7 Polymers

6 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

alkene unsaturated double bond C=C ethene propene CnH2n addition reaction hydrogenation hydration bromination bromine water decolourisation polymerisation monomer polymer poly(ethene) poly(propene)

Key terms covered in this Alkenes deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Hydrocarbons
Petroleum

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How to study this Alkenes deck

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