Combustion of Alcohols

Chemistry Industry Related Resources

Use of Chemical Calculations, Moles and Masses

Topic / Summary / Resources / Specifications
Lesson 1
Combustion of alcohols’ / Demonstrate methane bubbles
What is ‘good’ fuel
Combustion of alcohols’ Practical - burning methanol, ethanol, propan-1-ol and butan-1-ol
Calculations including extension
Reflection on the lesson / Teachers Notes
Picture
PowerPoint slide 2
Discussion
PowerPoint slide 3 - 9
Plenary Triangle
PowerPoint slide 10 – 23
Worksheet 1
Worksheet 2
Worksheet 3 / AQA Unit 3. 13.4 How much energy is involved in chemical reactions?
EDXEL C1 - E5.20 Demonstrate an understanding of the factors that make a good fuel, including: a how easily it burns c the comparative amount of heat energy it produces (calculations involving conversion to joules are not required)
OCR Gateway C3f: Energy
Describe, using a diagram, a simple calorimetric method for comparing the energy transferred in combustion reactions:
• use of spirit burner or a bottled gas burner
• heating water in a copper calorimeter
• measuring the temperature change
• fair tests.
Interpret and use data from simple calorimetric experiments related to the combustion of fuels to compare which fuel releases the most energy.
Lesson 2
Enthalpies of Combustion / Calculating enthalpy of combustion of methane
Calculate the enthalpy of combustion of the alcohol burned in lesson 1 (Higher Tier)
Self Assessment
Homework / Teachers Notes
Demonstrate or show video of the ‘Whoosh Bottle’.
PowerPoint slide 24 - 36
Worksheet 4
Plenary Triangle
Exampro - Home Work questions and Mark Scheme / AQA Unit 3. 13.4 How much energy is involved in chemical reactions?
EDEXEL C2 - 5.2 Define an exothermic change or reaction as one in which heat
energy is given out, including combustion reactions or explosions
5.4 Describe the breaking of bonds as endothermic and the making
of bonds as exothermic
5.5 Demonstrate an understanding that the overall heat energy
change for a reaction is:
a exothermic if more heat energy is released making bonds in
the products than is required to break bonds in the reactants
b endothermic if less heat energy is released making bonds in
the products than is required to break bonds in the reactants
5.6 Draw and interpret simple graphical representations of energy changes occurring in chemical reactions (no
knowledge of activation energy is required)
Explain why a reaction is exothermic or endothermic using the energy changes that occur during bond breaking and bond making.
Use the formula
energy transferred (in J) = m × c × _T to calculate:
• m = mass of water heated
• _T = temperature change.
Calculate the energy output of a fuel in J/g by recalling and using the formula:
energy per gram = energy released (in J) mass of fuel burnt (in g)
Lesson 3 (Brief version)
Consequences of Combustion of Fossil Fuels / Considering the social, economic and environmental consequences of using fuels.
Research & presentation activity
Homework questions
This lesson promotes more independent learning and may be preferable for more able students. / Teachers Notes
PowerPoint slide 37 – 41
PowerPoint slide 42-43
Worksheet 5 / AQA Unit 3 13.4 How much energy is involved in chemical reactions
• To consider the social, economic and environmental consequences of using fuels
EDEXEL C1- 1.9 Demonstrate an understanding of how small changes in the atmosphere occur through:
a volcanic activity
b human activity, including the burning of fossil fuels, farming and deforestation
Alternative Lesson 3
(Extended Version) / This lesson is an alternative to the above. This version looks at the environment in more depth and has a very detailed PowerPoint. This version may be preferable for less able students. / PowerPoint slides 44 - 57
Plenary Triangle

Lesson 1 Combustion of Alcohols – Teachers Notes

Teachers Notes

AQA 2011 Specification:

Unit Chemistry 3

13.4 How much energy is involved in chemical reactions?

Knowing the amount of energy involved in chemical reactions is useful so that resources are used efficiently and economically. It is possible to measure the amount of energy experimentally or to calculate it.

· To compare the energy produced by different fuels or food

· The relative amounts of energy released when substances burn can be measured by simple calorimetry, eg. by heating water in a glass or metal container. This method can be used to compare the amount of energy produced by fuels and foods.

Lesson 1

Starter: Demonstrate methane bubbles burning or show picture.

Main: Discussion – What is a ‘good’ fuel?

View PowerPoint ‘C.A.T.S. Introduction’

Practical: Introduce the Plenary Triangle

View ‘Combustion of alcohols’ Powerpoint, Pupil worksheet.

Conduct practical – burning methanol, ethanol, propan-1-ol and butan-1-ol

Calculations: View ‘Calculations’ on ‘Combustion of alcohols’ PowerPoint to support the calculations – including extension calculations.

Plenary – assess learning through Plenary Triangle – the Learning Objectives listed could be assessed using traffic lights, thumbs or smiley faces.

‘Reflection on the Lesson’ allows pupils to self-assess their learning.

Methane Bubbles

Heat of Combustion

Worksheet 1

You are comparing the energy released when fuels burn using the equipment below.

Diagram

Method

Record the mass of the fuel in the spirit burner.

Record the temperature of the water.

Burn the fuel for 2 minutes.

Record the final temperature.

Record the final mass.

BEFORE you carry out the practical you need to DESIGN YOUR RESULTS TABLE.

Calculations

Calculate the mass loss and the temperature rise.

Now calculate the temperature rise per gram of fuel burnt.

Conclusion

Which fuel releases the most energy per gram of fuel?

Evaluation

Identify the dependent, independent and control variables.

What are the sources of error in your experiment?

Heat of Combustion

Worksheet 2

Extension Calculations

How many moles of fuel were burnt?

Finally calculate the ENERGY RELEASED per mole of fuel burnt.

Conclusion

Which fuel releases the most energy per mole?

Worksheet 3

Reflection on the lesson

Look at your ‘Plenary Triangle’.

Which level or levels have you managed to complete?

List TWO things you have done this lesson that you are most pleased about:

1______

2______

Give ONE thing in the lesson you think you could improve upon: (hint - look at the plenary triangle for clues)

______

Lesson 2 Enthalpies of Combustion

AQA 2011 Specification:

Teachers Notes

Unit Chemistry 3

13.4 How much energy is involved in chemical reactions?

· Interpret simple energy level diagrams in terms of bond breaking and bond formation (including the idea of activation energy…)

· Higher Tier: to calculate the energy transferred in reactions, using simple energy level diagrams or supplied bond energies.

· During a chemical reaction:

o Energy must be supplied to break bonds

o Energy is released when bonds are formed

These changes can be represented on an energy level diagram

· In an exothermic reaction the energy released from forming new bonds is greater than the energy needed to break existing bonds.

Lesson

Starter: Demonstrate or show video of the ‘Whoosh Bottle’.

Main: Introduce the Plenary Triangle.

Discuss example of calculating enthalpy of combustion of methane on PowerPoint.

Pupils should attempt to calculate the enthalpy of combustion of the alcohol they burned in lesson 1 (Higher Tier)

Questions should be answered.

Extension Questions 2 and 3: How Science Works – Identifying sources of error such as the loss of energy during the experiment and the specific heat capacity of the beaker. Ideas could be shared (pair, share, review). There is an extinct ISA available from AQA directly related to this which could be conducted or used as a homework activity.

Answers could be peer assessed.

Self assessment of lesson objectives on Plenary Triangle.

Plenary: Use whiteboards to draw structure of different alcohols, energy level diagram for exothermic reaction, and balanced symbol equations.

Homework: AQA question from Exampro.

Enthalpies of Combustion

Worksheet 4

Questions

C.A.T.S. burn methane to heat up the natural gas from -33 oC to around 5 oC.

1. Try to write balanced equations for the complete combustion of methane, methanol, ethanol, propan-1-ol and butan-1-ol.

2. Are combustion reactions exothermic or endothermic?

3. Can you sketch an energy level diagram for a combustion reaction?

4. Calculate the theoretical enthalpy of combustion of the alcohol you burned last lesson.

5. Record the enthalpies of combustion of the four alcohols in a table – label the columns.

6. Plot a bar chart of the number of carbon atoms in each alcohol against the enthalpy of combustion.

7. Which from the four alcohols and methane releases the most heat per mole of fuel?

Bond energies:

C-C 348 kJ mol-1 C-H 413 kJ mol-1 C-O 358 kJ mol-1

O-H 463 kJ mol-1 O=O 498 kJ mol-1 C=O 805 kJ mol-1

Homework

(Ref: AQA Exampro)

Bond energies:

C-C 348 kJ mol-1 C-H 413 kJ mol-1 C-O 358 kJ mol-1

O-H 463 kJ mol-1 O=O 498 kJ mol-1 C=O 805 kJ mol-1

This equation shows the reaction between ethene and oxygen.

C2H4 + 3O2  2CO2 + 2H2O

The structural formulae in the equation below show the bonds in each molecule involved.

Use the three stages shown at (a), (b) and (c) below to calculate the nett energy transfer when the formula mass (1 mole) of ethene reacts with oxygen.

(a) Write down the bonds broken and the bonds formed during the reaction. (Some have already been done for you.)

(2)

(b) Calculate the total energy changes involved in breaking and in forming all of these bonds. (Some have already been done for you.)

(4)

......

(2)

(Total 8 marks)

Homework Mark Scheme

(Ref AQA Exampro)

(a) Bonds broken Bonds formed 2
number type number type
3 [O=O] 4 [O–H]

each for 1 mark

(b) Total energy change Total energy change 4
in breaking bonds in forming bonds
3 × 498 = 1494 4 × 464 = 1856

each for 1 mark

Total = 3758 Total = 5076

each for 1 mark

[N.B. credit e.c.f. (a)  (b) and (b)  (c)]

[8]

Lesson 3 Consequences of Combustion of Fossil Fuels

Teachers Notes3

AQA 2011 Specification:

Unit Chemistry 3

13.4 How much energy is involved in chemical reactions

· To consider the social, economic and environmental consequences of using fuels.

Lesson

Starter: Pupils to produce bullet points or a mind map of showing their ideas of environmental problems caused by the combustion of fossil fuels.

Main: Show the PowerPoint about the environmental considerations of C.A.T.S. about monitoring and control of emissions.

Pupils research an area of environmental concern and display their research in a 2 minute PowerPoint. Suggested research sites are listed in a PowerPoint.

Pupils share their research in groups of a minimum of 6 – one pupil for each research area.

Plenary: Each group of 6 agree on the three most significant things their team’s research has highlighted. These are shared with the class – possibly as post-its stuck on the board.

Worksheet 5

Read through the information given about wildlife conservation at the BP CATS terminal and answer the following questions:

1. Why is it important for companies like CATs to be involved in wildlife projects?

2. Give 2 examples of how CATs have encouraged wildlife to the site.

3. How does the Reedbed system treat waste water from the plant?

4. What are the advantages of using a Reedbed system?

5. What is the evidence that the CATs terminal has benefited wildlife in the area?