CIE A Level Chemistry

Revision Notes

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First teaching 2020

Last exams 2024

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3.1.1 Hydrocarbons & Alkanes

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Homologous Series

  • Organic chemistry is the chemistry of carbon compounds
  • Carbon forms a vast number of compounds because it can form strong covalent bonds with itself
  • This enables it to form long chains of carbon atoms, branched chains or cycles, and hence an almost infinite variety of carbon compounds are known
  • Carbon always forms four covalent bonds which can be single, double or triple bonds

Catenation in Carbon, downloadable IB Chemistry revision notes

There is an almost infinite variety of chains, branches and rings able to form

  • functional group is a specific atom or group of atoms which confer certain physical and chemical properties onto the molecule
  • Organic molecules are classified by the dominant functional group on the molecule
  • Organic compounds with the same functional group, but with each successive member different by CH2 are called a homologous series
    • Every time a carbon atom is added to the chain, two hydrogen atoms are also added, which is why the successive members differ by CH2

Hydrocarbons

  • Hydrocarbons are compounds that are made up of carbon and hydrogen atoms ONLY

 

An Introduction to AS Level Organic Chemistry Hydrocarbons and Non-Hydrocarbon, downloadable AS & A Level Chemistry revision notes

The diagram shows examples of hydrocarbons

Ethanol is NOT a hydrocarbon as the molecule also contains an oxygen atom and is not solely made up of carbon and hydrogen

Exam Tip

You must state that hydrocarbons are ‘only’ made up of C and H atoms if defining this term in an exam

Alkanes

  • A functional group is an atom or a group of atoms in an organic molecule, which determines the physical and chemical properties of the molecule
  • Alkanes are the simplest hydrocarbons with no functional group
  • They are made up of carbon and hydrogen atoms bonded to each other with single covalent bonds

An Introduction to AS Level Organic Chemistry Alkanes, downloadable AS & A Level Chemistry revision notes

Alkanes are compounds made up of carbon and hydrogen atoms only and contain no functional group

Homologous Series of Alkanes Table

Homologous Series of Alkanes, downloadable IB Chemistry revision notes

 

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Fran studied for a BSc in Chemistry with Forensic Science, and since graduating taught A level Chemistry in the UK for over 11 years. She studied for an MBA in Senior Leadership, and has held a number of roles during her time in Education, including Head of Chemistry, Head of Science and most recently as an Assistant Headteacher. In this role, she used her passion for education to drive improvement and success for staff and students across a number of subjects in addition to Science, supporting them to achieve their full potential. Fran has co-written Science textbooks, delivered CPD for teachers, and worked as an examiner for a number of UK exam boards.