New
New
Year 11
AQA
Higher

Chemical tests involving alkanes, alkenes and alcohols

I can use data to identify the functional group and predict the chain length for an alkane, alkene or alcohol.

New
New
Year 11
AQA
Higher

Chemical tests involving alkanes, alkenes and alcohols

I can use data to identify the functional group and predict the chain length for an alkane, alkene or alcohol.

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Lesson details

Key learning points

  1. A chemical test can identify the differences between alkanes and alkenes.
  2. Data from calorimetry and viscosity experiments can be used to predict the chain length of alkanes, alkenes & alcohols.
  3. As chain length increases, more energy is released during combustion.
  4. As chain length increases, the viscosity of alkanes, alkenes and alcohols increases.

Keywords

  • Homologous series - A homologous series of organic compounds have the same general formula, and show similar chemical properties and physical property trends.

  • Functional group - The functional group is the atom or group of atoms responsible for the way a compound reacts.

  • Calorimetry - Calorimetry is an experiment that can be used to measure the energy released from a fuel.

  • Viscosity - Viscosity is how easily a liquid flows. The higher the viscosity, the less easily a liquid flows.

Common misconception

Describing the colour change of bromine water with an alkene from orange to clear.

Coloured solutions can be clear if you can see through them. Colourless means it has no colour. Bromine water in the presence of an alkene changes from orange to colourless.

Molymods can be used to model how bromine can react with an alkene.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Sort the following alcohols into order of increasing chain length, starting with the shortest.
1 - methanol
2 - ethanol
3 - propanol
4 - butanol
5 - pentanol
Q2.
What name is given to the atom or group of atoms responsible for the way a compound reacts?
Correct Answer: functional group
Q3.
Match the following homologous series with the correct functional group.
Correct Answer:alkene,C=C

C=C

Correct Answer:alcohol,–OH

–OH

Correct Answer:carboxylic acid ,–COOH

–COOH

Correct Answer:ester,–COO–

–COO–

Q4.
Identify the molecule shown in the image.
An image in a quiz
methene
methane
methanol
Correct answer: ethene
ethane
Q5.
Which experiment is used to indirectly measure the energy released from the combustion of different fuels?
photosynthesis
crystallisation
distillation
Correct answer: calorimetry
Q6.
Which of the following statements about alkenes are correct?
Correct answer: alkenes contain a C=C double bond
alkenes are saturated molecules
the simplest alkene is methene
Correct answer: butene is an alkene containing 4 carbon atoms
Correct answer: the general formula of alkenes is $$\text{C}_{\text{n}}\text{H}_{\text{2n}}$$

6 Questions

Q1.
Which of the following is a test for unsaturation?
Add sodium carbonate and test for carbon dioxide.
Add hydrochloric acid and observe bubbling.
Correct answer: Add bromine water and observe a colour change.
Add lithium hydroxide and test the pH.
Q2.
Which of the following statements about chain length is correct?
Correct answer: As chain length increases, more energy is released during combustion.
As chain length increases, the same energy is released during combustion.
As chain length increases, less energy is released during combustion.
Q3.
Sort the following alkenes into order of decreasing viscosity, starting with the most viscous.
1 - pentene
2 - butene
3 - propene
4 - ethene
Q4.
Which of the following colour changes, if any, will be observed when bromine water is added to an alkene?
from colourless to orange
from clear to orange
Correct answer: from orange to colourless
from orange to clear
remains orange
Q5.
Which of the following colour changes, if any, will be observed when bromine water is added to the molecule shown in the image?
An image in a quiz
from colourless to orange
from clear to orange
from orange to colourless
from orange to clear
Correct answer: remains orange
Q6.
Which of the following molecules will decolourise bromine water?
Correct answer: C₂H₄
C₂H₆
Correct answer: C₃H₆
C₃H₈