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1CH0 · CP9.28CCore practical investigationsCore

CP9.28C: Comparing Four Alcohol Fuels

Pearson CP9.28C compares ethanol, propanol, butanol and pentanol by the temperature rise of a known water mass. Use the approved burners and heating arrangement and keep relevant geometry, water amount, starting conditions and mixing comparable. A comparison of only one or two fuels does not cover the full specified set.

35 min Video by Pearson UK & International Schools Core practical investigations
Pearson Edexcel (9-1) GCSE Chemistry core practical - combustion of alcoholsCurated by Kepler, not produced by us. Watch it before the notes below.
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Before you start

  • Use your teacher’s tier checklist: this overview can include Higher-only material, and is not a tier-specific revision list.
  • Pearson Edexcel separate GCSE Chemistry 1CH0. Preserve the specification’s core-practical reference and any explicitly required subparts.
  • Calculate a mass difference and distinguish temperature rise from energy transferred.
  • Use the centre’s approved supervised method, apparatus, heating and disposal arrangements. Written preparation does not replace performing and recording the practical activities.

Watch, pause, try

Video by Pearson UK & International Schools. The Pearson video develops the specified alcohol-comparison context. The RSC companion resource focuses on an ethanol setup; the written guide requires comparison of all four named alcohols.

Viewing focus: Compare the four specified alcohols using consistent measurements

After watching, attempt these questions before opening the answers. You can also use the written lesson below.

After watching 1: Which fuel set is specified for this Pearson comparison?

Show answer and reasoning

Ethanol, propanol, butanol and pentanol. Keep all four alcohol contexts.

After watching 2: Why measure fuel mass change?

Show answer and reasoning

A temperature rise alone does not give energy per gram of fuel. The denominator of an energy-per-mass comparison must be measured.

What you'll be able to do

  • Compare the four specified alcohols using consistent measurements
  • Calculate water-heating estimates and energy per gram
  • Evaluate heat loss, evaporation and incomplete combustion
1

Define a fair four-fuel comparison

Pearson CP9.28C compares ethanol, propanol, butanol and pentanol by the temperature rise of a known water mass. Use the approved burners and heating arrangement and keep relevant geometry, water amount, starting conditions and mixing comparable. A comparison of only one or two fuels does not cover the full specified set.

Measure burner-plus-fuel mass before and after the defined heating interval to estimate fuel mass lost. Record water temperatures and the chosen endpoint. A fixed heating time, a fixed temperature increase and a fixed fuel mass are different designs; state which quantities were controlled and which were measured.

2

Process the heat signal under a stated model

For a supplied water-heating model, q = mcΔT estimates energy received by the water. Use compatible units and the measured rise, then divide by the measured fuel mass change when comparing energy per gram. Do not compare only final temperatures when starting values or water masses differ.

The energy received by the water is less than a complete account of the fuel’s chemical energy in an imperfect classroom arrangement. Some transfers heat the apparatus or surroundings. Reporting a result in kJ g⁻¹ does not by itself make it a standard molar enthalpy of combustion.

AlcoholFuel mass lost / gWater temperature rise / K
Ethanol0.2505.0
Propanol0.3007.0
Butanol0.3509.0
Pentanol0.40010.0
Scroll horizontally to see the full code or table.
Original illustrative data with 100 g water in each comparison. Use the supplied heat-capacity model and retain the experimental limitations; these are not reference combustion values.
3

Explain departures without forcing a trend

Air movement, flame position, soot, incomplete combustion and heat exchange can affect the result. Fuel evaporation during handling can contribute to mass loss without the corresponding measured heating. Independent repeats and appropriate timing and shielding can improve a controlled comparison.

A result that differs from an expected chain-length pattern should prompt evaluation of the actual measurements and model. It does not justify deleting the point or claiming that every difference is molecular structure alone. Distinguish the water-heating observation from an intrinsic fuel value measured under fully controlled conditions.

4

Worked applications

Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.

Example 1A burner loses 0.300 g while 100 g water rises by 6.0 K. With c = 4.18 J g⁻¹ K⁻¹, estimate energy received per gram of fuel lost.
1Water energy = 100 × 4.18 × 6.0 = 2508 J.
22508/0.300 = 8360 J g⁻¹.
Answer
8.36 kJ g⁻¹ under the stated water-heating and mass-loss assumptions.
Example 2Why is a measured mass loss not necessarily exactly the mass that combusted usefully to heat the water?
1Some fuel can evaporate during handling.
2Combustion may be incomplete, and not all transferred energy reaches the water.
Answer
The result requires a stated mass-loss and heat-transfer model, with specific limitations.
Example 3Using the illustrative table, compare water-heating energy per gram for butanol and pentanol. Use 100 g water and c = 4.18 J g⁻¹ K⁻¹.
1Butanol: 100 × 4.18 × 9.0 / 0.350 ≈ 10749 J g⁻¹.
2Pentanol: 100 × 4.18 × 10.0 / 0.400 = 10450 J g⁻¹.
3A larger temperature rise alone does not set the per-gram ranking.
Answer
About 10.75 kJ g⁻¹ for butanol and 10.45 kJ g⁻¹ for pentanol in these original illustrative measurements, not universal combustion values.

Common mistakes to avoid

Calling a classroom water-heating estimate a complete intrinsic combustion value.
Evaluate apparatus and surroundings transfers.
Forcing every measured point into a predicted chain-length trend.
Retain and evaluate the actual data.

Key takeaways

  • You can compare the four specified alcohols using consistent measurements.
  • You can calculate water-heating estimates and energy per gram.
  • You can evaluate heat loss, evaporation and incomplete combustion.

Apply it in an exam

Question 1: Using the illustrative table, compare water-heating energy per gram for butanol and pentanol. Use 100 g water and c = 4.18 J g⁻¹ K⁻¹.

Show answer and reasoning

About 10.75 kJ g⁻¹ for butanol and 10.45 kJ g⁻¹ for pentanol in these original illustrative measurements, not universal combustion values.

  • Butanol: 100 × 4.18 × 9.0 / 0.350 ≈ 10749 J g⁻¹.
  • Pentanol: 100 × 4.18 × 10.0 / 0.400 = 10450 J g⁻¹.
  • A larger temperature rise alone does not set the per-gram ranking.

Explore further

Return to this tomorrow

Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.

  • Why measure fuel mass change?
  • What does mcΔT describe in the stated model?

Test yourself

Answer a few questions, then review anything you missed.

Next step

Keep practising

Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.

Browse practice topics

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