Chemistry 11–12 · Year 11

Calorimetry of ethanol combustion: measuring the enthalpy of combustion and explaining the shortfall

Module 4: Drivers of Reactions

Practical, model not builtMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

The heat released by burning a weighed mass of fuel is captured by a known mass of water; the enthalpy of combustion per mole follows, and the gap from the accepted value measures heat loss.

Safety card

Medium riskLearners carry it out, with a teacher supervising

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

ethanol flame and hot can
spilt ethanol can ignite
refilling a warm burner

Controls

burner capped to extinguish, never blown
refilling only by the teacher when cold
hair tied back, eye protection
heat-resistant mat

Note

NSW Department of Education Chemical Safety in Schools (CSIS) package, 2021 Technical Update: Section 1.7 (risk assessment) and Volume 2 Appendix D (generic assessment advice and DoE chemical categories); record a RiskAssess (riskassess.com.au) risk assessment before the lesson and check the school's hazardous chemical register (CSIS Section 1.9) for local restrictions.

What you need

Spirit burner with ethanol and cap
Aluminium can or copper calorimeter, or a 250 mL conical flask, holding 100.0 mL water
Retort stand, clamp, draught shield (a large tin with holes or a cardboard screen)
Thermometer reading to 0.1 degrees Celsius or a temperature probe
Balance reading to 0.01 g
Measuring cylinder 100 mL

How to do it

Measure 100.0 mL of water into the can; clamp the can so its base is 2 cm above the wick; fit the draught shield.
Weigh the capped burner; record the starting water temperature.
Light the burner and stir the water gently until the temperature has risen by 20.0 degrees Celsius; cap the flame at once and record the highest temperature reached.
Reweigh the capped burner; calculate the mass of ethanol burned.
Calculate q = m c delta T for the water, the moles of ethanol burned, and the enthalpy of combustion in kJ/mol; repeat twice and average.
Compare with the accepted value, calculate the percentage captured, and list the losses in order of size; repeat with the draught shield removed to measure its effect.
Enter the results in the simulation to see how the captured fraction and the can's heat capacity change the reading.

What you should see

Ethanol releases 1367.6 kJ/mol (29.7 kJ/g; NIST WebBook). If every joule entered the water, 0.50 g of ethanol would warm 100 g of water by 35.5 degrees Celsius; if a calorimeter captures between 30 and 60 percent of the heat, a 20 degree rise needs 0.47 to 0.94 g of ethanol and the learner reports 410 to 821 kJ/mol. A copper can with a draught shield gives the highest fraction; a glass flask without a shield the lowest. Soot on the can shows incomplete combustion, which lowers the result further.

What changes

What you change: calorimeter arrangement (draught shield present or absent, can material)
What you measure: enthalpy of combustion obtained (kJ/mol) and the percentage of the accepted value
What you keep the same: water mass
temperature rise of 20 degrees
burner height
same fuel

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A low result means the accepted value is wrong (it means heat escaped; the losses can be listed and reduced).
The energy comes from breaking the bonds in ethanol (bond breaking absorbs energy; the release comes from forming the stronger bonds in CO2 and H2O).
Doubling the water halves the energy released (the fuel releases the same energy; the temperature rise halves).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document)CH11-11 CH11/12-5 CH11/12-6
Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document); a Working Scientifically outcome not among those the syllabus targets in Module 4, which it allows in any moduleCH11/12-3
Chemistry 11-12 Syllabus (2025), NESA; implemented from 2028, not yet taughtCH-11-03 CH-11WS-03 CH-11WS-05
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities