Hydrocarbons: Structure, Properties and Common Examplea

The presentation introduces hydrocarbons, the simplest organic compounds composed only of carbon (C) and hydrogen (H) atoms. It explains their structural and condensed formulas, highlighting how molecular composition and bonding determine the properties of each type.

The slides classify hydrocarbons into three main groups:

Alkanes – single-bonded hydrocarbons (saturated), ending in –ane (e.g., methane, butane, octane).

Alkenes – hydrocarbons containing at least one double bond, ending in –ene (e.g., ethene, pentene).

Alkynes – hydrocarbons with at least one triple bond, ending in –yne (e.g., ethyne or acetylene).

It also discusses the physical properties of hydrocarbons, emphasizing that:

The state of matter depends on molecule size (smaller molecules are gaseous, larger ones are liquid or solid).

Boiling point increases with molecular size due to stronger intermolecular interactions.

The latter part contains assessment questions that test understanding of:

Types and examples of hydrocarbons

Bonding characteristics

Physical properties like boiling points

Common uses of hydrocarbons such as fuels and industrial materials

1. Hydrocarbons Organic compounds that contain carbon (C) and hydrogen (H) atoms only

2. Structural formula – molecular formula that indicates the atoms present and the bonding sequence of the atoms

3. Condensed formula – molecular formula that indicates the bonding sequence without showing all the bonds CH 3 CH 3 CH 2 =CH 2 CH CH

4. Boiling point – the temperature at which a liquid evaporate or becomes vapor

5. Table 1. Alkanes Phase Boiling Point (°C) Gas -162 Gas -89 Gas -42 Gas -0.5 Liquid 36 Liquid 69 Liquid 98 Liquid 126

6. Table 1. Alkenes Phase Boiling Point (°C) Gas -104 Gas -47 Gas -6 Liquid 30 Liquid 63

7. Table 1. Alkynes Phase Boiling Point (°C) Gas -84 Gas -47 Gas 8.08 Liquid 40.2

8. 3 Groups of Hydrocarbon Alkanes – have single bonds in the compound - end in – ane - known as saturated hydrocarbons because additional H atoms can no longer bond in the atom Ex. Methane – used as fuel for cigarette lighters and LPG - mixed with other fuel for vehicle Butane – used as fuel, blended with other HC to produce LPG - fuel for cigarette lighter (blue) Octane – component of gasoline

9. 3 Groups of Hydrocarbon Alkenes – have one or more carbon-carbon double bonds - end in – ene Ex. Ethene (CH 2 CH 2 ) – simplest alkene Pentene – component of gasoline

10. 3 Groups of Hydrocarbon Alkynes – have at least one carbon-carbon triple bond - end in – yne Ex. Ethyne (C 2 H 2 ) – known as acetylene used in flame torch for welding iron.

11. * The physical state of the hydrocarbon depends on the size of the molecule. It is gas when the molecule is small and becomes liquid as the molecule becomes bigger.

12. * The bigger the molecule the higher the boiling point because they interact more.

13. Which alkane would likely to have a very low boiling point? A. Butane B. Hexane C. Pentane D. Propane

14. 2. What is the common use of methane? A. fuel B. Fertilizer C. disinfectant D. artificial ripening agent

15. 3. To which group of hydrocarbons does the molecule with the structure below belong? A. alkane B. alkene C. alkyne D. None of these

16. 4 . Which hydrocarbon compound has a triple bond in the molecule? A. octane B. methane C. ethene D. ethyne

17. 5. How many types of bonds are there in the following hydrocarbon compound? A. 1 C. 3 B. 2 D. 4

18. 6. A gaseous hydrocarbon used as fuel for cigarette lighter with blue light A. octane B. methane C. ethane D. butane

19. The phase of hydrocarbons is gas when the molecules is ______ A. small B. long C. heavy D. dense

20. Bigger molecules of hydrocarbons tend to become _____ A. solid B. plasma C. liquid D. gas

21. 9. The bigger the molecules the higher the boiling point because _____ A. they interact more. B. they interact less. C. they become less dense D. None of the above

22. 10. The size of the structures of the compounds is increasing because the compounds become _____ A. bigger B. longer C. shorter D. A and B