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4.19 - 4.22 Alkanes

 4.19 Some saturated hydrocarbons

butane bottles
Butane is used as a fuel. It is the fourth member of the alkanes.

The Alkane series is a family of hydrocarbons.  The technical name for this sort of  "family" is a "homologous series" The alkane molecules contain atoms of hydrogen and carbon only.

The general formula for the alkanes is CnH2n+2

​Assumed background knowledge

4.1 - 4.7 Organic chemistry

Organic chemistry is concerned with the compounds of the element carbon. Here we introduce the basic principles of this huge topic. 
https://www.mychem.co.uk/index.php/igcse-chemistry/organic-chemistry/introduction-to-organic-chemistry

4.7 - 4.9 Crude oil

Crude oil is a major source of raw material for the petrochemical industry. 
https://www.mychem.co.uk/index.php/igcse-chemistry/organic-chemistry/crude-oil

 4.19- 4.21 Activity 1. From one to ten

 Students should:

  • 4.19 know the general formula for alkanes
  • 4.20 explain why alkanes are classified as saturated hydrocarbons
  • 4.21 understand how to draw the structural and displayed formulae for alkanes with up to five carbon atoms in the molecule, and to name the unbranched-chain isomers

Use the first 3 minutes and 20 seconds of  video here to help you answer the questions below: 

  1. Why are alkanes regarded as saturated hydrocarbons?
  2. How many covalent bonds do a carbon atom need to form in order to become stable?
  3. What is methane also known as?
  4. What is methane used for?
  5. What is the formula for ethane?
  6. What is the formula of pentane?
  7. And Decane?
  8. what is the general formula for the alkanes?
  1. The alkanes are regarded as saturated hydrocarbons because they only have single bonds between their carbon atoms.
  2. A carbon atom need to form four bonds in order to become stable?
  3. Methane also known as natural gas
  4. Methane is used for heating and cooking
  5. The formula for ethane is C2H6
  6. The formula of pentane is C5H12
  7. The formula of Decane is  C10H22
  8. The general formula for the alkanes is  CnH2n+2

 4.22 Activity 2. Time for a substitution

 Students should:

  • 4.22 describe the reactions of alkanes with halogens in the presence of ultraviolet radiation, limited to mono-substitution knowledge of reaction mechanisms is not required

Here we look at the way alkanes react with halogens ( for example Chlorine Cl2). When chlorine is mixed with methane ( CH4 ) nothing happens until the mixture is irradiated with ultraviolet radiation.

Study the animation before answering the questions below:

  1. ​Use the animation to construct an equation for the reaction shown
  2. What does the ultraviolet radiation do to the chlorine molecule?
  3. What is the name of the two products?
  4. Why is this process called substitution?
  5. Write an equation for the reaction.

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