Heat energy from alcohols
This experiment compares the amounts of heat energy produced by burning various alcohols.
Read our standard health & safety guidance
Lesson organisation
This experiment is suitable for pre-16 students, possibly as an introduction to a topic on fuels. It can be taken further if used with post-16 students who can calculate values for enthalpy changes of combustion, with subsequent discussion about heat losses and incomplete combustion.
The alcohols should be provided in labelled spirit burners ready to use. If each group investigates one alcohol, the experiment can be done in around 20 mins. It is better if each spirit burner is used by more than one group of students. Variation of results will add substance to a discussion about errors.
Apparatus and chemicals
Eye protection
Each group of students requires:
Retort stand and clamp
Conical flask (150 cm3 or larger)
Measuring cylinder (100 cm3)
Thermometer (-10 °C to +110 °C)
Access to balances, preferably several, to avoid queuing.
Groups require access to spirit burners (see note 1), with wicks and caps, containing the following highly flammable alcohols, which are also volatile and have low flash points.
Methanol (Highly Flammable, Toxic)
Ethanol (Highly Flammable)
Propan-1-ol (Highly Flammable, Irritant)
Propan-2-ol (Highly Flammable, Irritant)
Butan-1-ol (Flammable, Irritant, Harmful)
Technical notes
Methanol (Highly Flammable, Toxic) Refer to CLEAPSS Hazcard 40B
Ethanol (Highly Flammable) Refer to CLEAPSS Hazcard 40A
Propan-1-ol (Highly Flammable, Irritant, Harmful) Refer to CLEAPSS Hazcard 84A
Propan-2-ol (Highly Flammable, Irritant, Harmful) Refer to CLEAPSS Hazcard 84A
Butan-1-ol (Harmful) Refer to CLEAPSS Hazcard 84B
1 Suitable spirit burners are hard to come by. Ideally they should be small, with a capacity of 50 cm3 or less. Pictures and information in suppliers' catalogues can be misleading. If capacity is more than 50 cm3, reduce it, for instance by packing with mineral wool, or partially filling with epoxy. Refer to CLEASPSS L195 Safer chemicals, safer reactions. One possible source is
A.J.Cope, 11/12 The Oval, Hackney Road, London, E2 9DU
Tel: 0207 729 2405 Fax: 0207 729 2657
Procedure
a Measure 100 cm3 of cold tap water into a conical flask.
b Clamp the flask at a suitable height so that a spirit burner can easily be placed below.
c Weigh the spirit burner (and cap) containing the alcohol and record this mass and the name of the alcohol.
d Record the initial temperature of the water in the flask.
e Place the spirit burner under the flask and light the wick.
f Allow the alcohol to heat the water so the temperature rises by about 40 oC.
g Replace the cap to extinguish the flame.
h Re-weigh the spirit burner and cap, and record this mass.
i Work out the mass of alcohol used.
j Using a fresh 100 cm3 of cold tap water, repeat the experiment with another alcohol.
Teaching notes
Get the class to record and share the results. Do not be surprised if groups get different answers for a given alcohol. Heat losses will almost certainly vary considerably.
Subsequent discussion depends on the level of the students’ experience.
Student questions
Here are some possible questions to ask students.
1 Which alcohol produces the most energy per gram?
2 Which alcohol produces the most energy per mole?
3 Write equations for the complete combustion of each alcohol.
4 Propan-1-ol and propan-2-ol are isomers (same molecular formula, different structures) Do they produce the same amount of heat on combustion?
5 Does all the heat produced by combustion go into raising the temperature of the water?
6 Is it possible that combustion may be incomplete, giving carbon monoxide amongst the products? (Stress the dangers of this.)
7 Alcohols can be used as a substitute for hydrocarbon fuels, and so methods of producing alcohols are very important. What process converts sugar into alcohol - and carbon dioxide?
Health and Safety checked, September 2007
Web Links
This website contains general information.
www.freestudentstuff.co.uk/GCSE_Chemistry_-_Alcohols_Coursework.htm
Updated 21 Feb 2008Average rating: 
3 out of 5
Your reviews
I also designed a similar experiment.
I think it was important to use a good conductive container like a coke can instead of a conical glass beaker.
Also, some measures should have been taken for avoiding the loss of heat - for example - you could have used some aluminium foil to sheath the apparatus in order to relfect the radiated heat.
Submitted by: Perola on 17 April 2008
You should list possible error sources and how to minimize them.
Submitted by: husna on 18 December 2008
I plan to limit the experiment to three alcohols, encouraging students to get a reproducible result with just one of these alcohols. We will then pool the results.
Problems such as incomplete combustion and heat loss can then be discussed using reasonable data (I hate trying to make any sense of carelessly collected data). This should help to develop our students' experimental skills, and give them the idea that care and accuracy are important aspects of practical work.
Submitted by: Mike Carrington on 18 December 2008
MORE VARIETY OF PROBLEMS THAT CAN BE SOLVED FOR EACH EXPERIMENT
Submitted by: jennifer jessop on 18 March 2009
Answers?
Submitted by: Hayley on 5 November 2009
The flask could be coated with aluminium foil to limit heat loss.
The experiment could be done in a tin can also to limit heat loss.
Submitted by: Thierry on 10 December 2009
I am deeply sorry to inform that this experiment is the worst experiment ever! Poorly constructed methods and procedures. This experiment should be deleted from this site once and for all.
Submitted by: Mr Taylor Lautner on 13 February 2010
Just wondering what the screw-on top part is called; the part that the wick is fed through.
Submitted by: Alex on 3 June 2010
Very good
Submitted by: Anna Skeen on 21 January 2008