Name:
G9 Integrated Science – Comparison of fuels LAB
In your groups, perform the experiment outlined below. Try to repeat the experiment with as many
different alcohols as you can in the time allowed. Think carefully about how you will record your data.
Aim
The aim of this experiment is to find out whether there is a relationship between the molecular mass of
liquid fuels (you will use alcohols) and the amount of energy they release when burned (combusted).
Alcohols are organic compounds. The names and formulas of the ones you will use today are as follows:
Name of alcohol
Methanol
Ethanol
Propanol
Butanol
Chemical formula or molecular formula
CH4O
C2H6O
C3H8O
C4H10O
Molecular mass
32
46
60
74
Some extra information:
Molecular mass is the mass of one molecule of a compound. It is found by adding up all of the atomic
masses of the atoms in that compound. Atomic masses can be found from a copy of a Periodic Table.
Molecular masses and atomic masses do not have any units.
e.g. Ethanol has the formula C2H6O.
Each C has an atomic mass of 12, each H has an atomic mass of 1 and oxygen has an atomic mass of 16.
So the molecular mass of C2H6O = (2 x 12) + (6 x 1) + (1 x 16) = 46
Hypothesis
Make a prediction about what you think the results might be.
As the molecular mass of the alcohol burned increases …………………………………………………………………………………
…………………………………………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………………………………………..
Can you sketch what the graph might look like if we plot molecular mass on the x-axis and energy released
per gramme on the y-axis?
Procedure
Beaker
Fuel
HEALTH & SAFETY: Wear eye protection
1. Clamp the beaker at a suitable height to allow room for the spirit burner to be placed below. Allow a
gap of around 2-5 cm between the base of the flask/can and the top of the spirit burner. This gap may
need to be adjusted depending on the height of the flame.
2. Using the measuring cylinder, fill the beaker with 100 cm3 of water.
3. Using the thermometer, measure and record the initial temperature of the water.
4. Take the mass of the spirit burner (and cap) containing the fuel and record the initial mass and name of
the fuel in a suitable table.
5. Place the spirit burner on the heat-resistant mat under the beaker, remove the cap, and light the wick.
6. Allow the fuel to heat the water for a fixed time of 5 minutes. Use a glass rod or the thermometer to stir
the water gently whilst the fuel burns.
7. Replace the cap on the spirit burner to extinguish the flame.
8. Record the final temperature of the water using the thermometer. Work out the temperature change.
9. Reweigh the spirit burner and cap. Work out the mass of fuel used.
10. Repeat the experiment for different fuels using 100 cm3 of fresh cold water each time.
Data Collection
Record all of your raw data (qualitative and quantitative; ask your teacher what this means) in a suitable
table neatly on a separate piece of file paper. Write in ink!
If you have a laptop computer you may also record your data in a suitable word-processed table.
Remember
 Draw a clear raw data table that includes initial temperature, final temperature, initial mass and
final mass for each of the fuels you tested.
 Don’t forget to state clearly in the column heading what that column represents, and remember the
units.
 Give a clear, descriptive title for your data table.
Data Processing and Presentation
You will use the formula q = m x c x ΔT to calculate the amount of energy given off by each fuel. Here is a
sample calculation:Initial temperature = 20°C
Final temperature = 35°C
Temperature change = 35 – 20 = 15°C
Initial mass = 5.32 g
Final mass = 4.48 g
Mass change = 5.32 – 4.48 = 0.84 g
Amount of energy given off:
q = mass of water x specific heat capacity of water x ΔT
q = 100g x 4.2J/g/°C x 15°C
q = 100 x 4.2 x 15 = 3200 J
This is the amount of energy in 0.84g. We need to find out the amount of energy in 1g.
Amount of energy in 1g = 3200 J = 3800 J
0.84 g
Remember
 Draw a clear processed data table that includes the type of fuel, molecular mass, the temperature
change, the mass change and the amount of energy given out.
 Remember title, correct column headings and units.
 Check your data is given to an appropriate and consistent level of accuracy.
 Draw a scatter plot, with molecular mass on the x-axis and amount of energy given off per gramme
on the y-axis. Draw a best-fit line through your points.
 Make sure your graph has a suitable title and that the axes are correctly labeled with units.
Conclusion and Evaluation
Remember
Conclusion
 Write a clear and detailed conclusion that is based on the correct interpretation of your results.
 State whether your data supports your hypothesis or not.
 Try to explain why some fuels are better than others for giving out heat energy.
 Look up energy content per gram for each of the types of fuels you tested. How does your data
compare to these values?
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
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Evaluation
List all the weaknesses and sources of error in your experiment.
For each weakness, discuss how it might have had an impact on your data, and whether it was a
major or relatively minor error.
For each weakness suggest a specific and realistic improvement that would improve this experiment
next time.