Homologous series, naming and saturation
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Millions of compounds, a few families
- What is a homologous series?
- Four series to know
Read the transcript of the teaching part
Last time
Before we start: last time, in Petroleum and cracking, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Millions of compounds, a few families
Carbon makes millions of compounds, from petrol to plastics to perfume. You cannot learn them one by one. But they fall into families, called homologous series, where every member behaves in a similar way. Learn the family and you can predict hundreds of compounds, and even give them a name.
What is a homologous series?
A homologous series is a family of compounds with the same functional group and the same general formula. Neighbouring members differ by CH 2. That is, one more carbon and two more hydrogens. They have similar chemical properties, and their physical properties change in a regular way, such as the boiling point rising.
Four series to know
Alkanes: C n H 2n plus 2. Alkenes, with a C=C double bond: C n H 2n. Alcohols, with the OH group: C n H 2n plus 1 OH. Carboxylic acids, with the COOH group: C n H 2n plus 1 COOH.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Homologous series · Naming organic compounds · Formulae, functional groups and homologous series.
The whole chapter: Organic Chemistry, Organic Chemistry.
Chapter 11: Organic chemistry
- Homologous series, naming and saturation 5 min
- Petroleum and cracking 5 min
- Reactions of alkanes and alkenes 5 min
- Addition polymers 6 min
- Ethanol: manufacture, combustion and oxidation 6 min
- Esters, condensation polymers and proteins 6 min
Also for IGCSE Chemistry 0620
Which topics come up most in IGCSE Chemistry 0620 past papers, counted from every paper since 2004.