2. Topic 6 Hydrocarbons

3. Aims: Discuss the Alkanes, which are a family of hydrocarbons. The name for the first eight alkanes. The structural formula of the first eight alkanes. The molecular formula of the first eight alkanes. The general formula for the alkane family.

4. Hydrocarbons Hydrocarbons are compounds which contain only the elements carbon and hydrogen. There are 3 hydrocarbon sub-groups: –Alkanes –Alkenes –Cycloalkanes

5. Same second name Homologous series Look similar

6. Alkanes Very important substances. Contain covalent bonds. Remember each carbon must from 4 bonds. All alkanes end in ‘ane’. Below are some of the uses of the alkanes: AlkaneUses Methane(natural gas) for cooking and heating PropaneUsed in gas cylinders for homes ButaneSold in blue cylinders as camping gas OctaneA component of petrol

7. Methane CH 4

8. Ethane C2H6C2H6

9. Propane C3H8C3H8

10. Methane Ethane Propane Butane Pentane Hexane Heptane Octane CH 4 C2H6C2H6 C3H8C3H8 C 4 H 10 C 5 H 12 C 6 H 14 C 7 H 16 C 8 H 18 Chemical Formula Full Structural Formula Name of Alkane Shortened Structural Formula CH 4 CH 3 CH 2 CH 3 CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3

11. The chemical of molecular formula tells you the number of carbon and hydrogen atoms in each molecule. The full structural formula shows relative position of the atoms in the molecule and the bonds holding the atoms together. The shortened structural formula does not show all of the bonds in the molecule.

12. Molecules that belong to the Alkane family only contain carbon to carbon single bonds. They are saturated hydrocarbons because the bonds between the carbons are saturated (single). The smaller alkanes are gases, but as they increase in size they become liquids and eventually solids. As the length of the alkane chain increases from methane  octane, their melting points and boiling points also increase. (see pg 6 of data booklet)

13. C n H 2n+2 Alkanes – Homologous series The alkanes are a homologous series. This means that: 1.All alkanes can be represented by a general formula which is: 2.They all have similar chemical properties 3.There is a link between their physical properties and their melting and boiling points.

14. The following rhyme might help you to remember the order of the hydrocarbons. MMonkeys EEat PPeanut BButter PPieces HHorses HHave OOats