Hydrocarbons
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24/08/2014. Hydrocarbons. L.O. I know what a hydrocarbon is and can name and draw the structural and molecular formula of the first six alkanes. Carbon: Organic Chemistry. Carbon is an unusual atom in that it is able to form very strong covalent bonds with other carbon atoms.

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Hydrocarbons

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24/08/2014

Hydrocarbons

L.O.

  • I know what a hydrocarbon is and can name and draw the structural and molecular formula of the first six alkanes.


Carbon: Organic Chemistry

  • Carbon is an unusual atom in that it is able to form very strong covalent bonds with other carbon atoms.

  • When we then include it’s ability to also bond with other elements we open up the possibility of the highly diverse and complex molecules (like DNA) that have led to the possibility of life.

  • Because of this, the chemistry of carbon containing compounds is often called organic chemistry.


Alkanes

  • A hydrocarbon consists of carbon and hydrogen only and every carbon has four single covalent bonds.

  • The simplest hydrocarbons form a series of compounds known as the alkanes.


H

H

C

H

H

Formulae and Models of Alkanes

  • Although normal chemical formula - like C5H12 - are used to describe alkanes they do not convey which atom is joined to which other atom.

  • To get around this we often used displayed formula to describe organic molecules.

  • Displayed formula show which 4 atoms each carbon is bonded to but even these do not show the actual 3D shapes. For that we use models.

methane, CH4


Copy and complete the following tablebut make the ‘displayed formula’ the 3rd column.


H

H

C

methane, CH4

H

H

H

H

ethane, C2H6

C

C

H

H

H

H

H

H

H

propane, C3H8

C

C

H

C

H

H

H

H

Displayed formula Alkane Molecular formula


butane, C4H10

H

H

H

H

C

C

C

H

H

C

H

H

H

H

pentane, C5H12

H

H

H

H

H

C

C

C

H

C

C

H

H

H

H

H

H


H

H

H

H

H

H

hexane, C6H14

C

C

H

C

C

H

C

C

H

H

H

H

H

H

Notice

the carbon chain

is not really

straight

and so on…………


  • The names of the 4 simplest alkanes are methane, ethane, propane and butane.

  • After that the names are systematic (like the words used to describe geometric shapes.) e.g.

    • 5 carbons = pentane C5H12

    • 6 carbons = hexaneC6H14

    • 7 carbons = heptaneC7H16

    • 8 carbons = octaneC8H18

    • 9 carbons = nonaneC9H20

    • 10 carbons = decaneC10H22

      Work out a general formula for the alkanes e.g. Cn H ????


The general formula of the alkanes is

CnH2n+2


In the backs of your books:-

Come up with an Mnemonic to remember the first 6 alkanes

e.g. Myvery easy method just speeds up naming planets.

Michael Eats Pizza But Prefers Hash-browns


Activity

  • What will be the formula for alkanes containing the following numbers of carbons?

C12H26

C16H34

C31H64

C19H40


Bonding in Alkanes

Alkanes contain atoms held together by single covalent bonds.

In the formula displayed we show these bonds as a single line.

Each line is really a pair of shared electrons


Which of these is an alkane?

  • C6H14

  • C4H8

  • C12H24

  • C102H204


The formula of the alkane with 15 carbons is?

  • C15H30

  • C15H60

  • C15H32

  • C15H28


Hydrocarbons contain only which two elements?

  • Carbon and electron

  • Carbon and water

  • Carbon and hydrogen

  • Carbon and oxygen


The bonds in a hydrocarbon are what type?

  • Metallic

  • Ionic

  • Complex

  • Covalent


Which is the simplest hydrocarbon?

  • Methane

  • Decane

  • Ethane

  • Butane


Which is alkane has 6 carbons?

  • Heptane

  • Hexane

  • Hectane

  • Hoptane


What is the molecular formula of ethane?

  • C3H8

  • C4H10

  • C2H6

  • C6H14


How many carbons does propane have?

  • 6

  • 3

  • 2

  • 5


Bingo

1. Alkanes9. butane

2. Methane10. covalent

3. C2H611. propane

4. Carbon12. ethane

5. Hydrogen13. electron

6. Four14. one

7. Three15. two

8. Six16. five


Homework

Complete sheet on the alkanes.


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