To compare the efficiency of different alcohols as fuel sources

         

O2        →        4 CO2  + 5 H2O

                

H        H        H        H

H        C        C        C        C        O        H

        H        H        H        H

        

Heat of Combustion = Energy in – Energy out

                                  = 8566 – 10550

                            = -1984 kJ / Mole

Prediction

The following table shows the heat of combustion for each of the 4 alcohols.

I predict that according to my table butanol will have the greatest weight loss as it takes the least amount of energy to heat it therefore it will be the first to begin giving out heat in the two. Ethanol will have the smallest weight change as it takes the most energy to burn which means it will release the least energy within the 2 minutes. I also predict that butanol will have the largest temperature change as it burns quicker and will heat the water up more within the 2 minutes. On the whole I believe that at this stage, theoretically butanol will turn out to be the most efficient.

Fair test

To keep my experiment fair here is a list of the constants:

• The amount of water in the calorimeter (100ml)
• This distance from the top of the spirit burner to the bottom of the calorimeter. (3cm)
• Leave the spirit burner burning from the same amount of time for each alcohol. (2min)

 

This is a list of the things I will keep the same:

• The alcohol in the spirit burner e.g. methanol, Ethanol, butanol, propanol)

• The amount of alcohol is specific to each burner used

Apparatus

• Clamp
• Copper Beaker
• Clamp stand
• Boss
• Spirit burner x4
• Heat proof mat
• 100cm3 measuring cylinder
• Water
• Stop clock
• Weighing scales
• Thermometer
• Bunsen burner
• Splint

Diagram

Method

1. Set up equipment like in the diagram
2. Measure 100cm3 of water in the measuring cylinder and pour it into the copper calorimeter
3. Record the temperature of the water
4. Choose a spirit burner; make a note of the alcohol inside and the mass with the lid on. Light the spirit burner and place under it under the copper beaker
5. Stir the water gently all the way through the experiment with the thermometer
6. After 2 minutes record the temperature of the water and the mass of the spirit burner with the lid and fuel (Note the timing is incorporated into my experiment because I lost my results and I could only get one from another science group. Who used timing in their experiment)
7. Put fresh water into the copper beaker and repeat all the steps for all the fuels 3 times.

(oC)

Results

Conclusion

The results that I found out are not what I predicted. I predicted that Butanol would loose the most energy. But clearly propanol has the greatest loss. My results indicate that propanol had the greatest loss by a large margin; I think external factors affected this experiment and if it was done under controlled conditions butanol would have had the greatest mass loss. I said that ethanol would have had the smallest change in weight this was proven I have drawn a graph to show this point. Also I have drawn a graph to show that butanol and propanol had the greatest temperature loss. My other graph shows that butanol and propanol had the greatest temperature change, which supports my prediction because I said that butanol would have the greatest temperature change. Another thing that my graph shows is that the presence of too many carbon atoms the reaction slows down and if there are too few carbon atoms then the heat of combustion also decreases, The best amount of carbon atoms is 2 this is illustrated by my graph.

Evaluation

I think my experiment was a success I had no problems and my prediction was half right. My prediction could have been proven to be correct. If I had repeated results a few more times Which would have given me a larger set of results and a more accurate total, some of the results could have been down to human error such as not setting the stopwatch. I have only one anomalous result this is the first test of ethanol, which is 1.5; this reading is much higher than in the other two ethanol readings. This is only a small part of my overall experiment I don’t think it would have had great effect on my overall results.  I think this problem is due to human fault no any inaccuracies with the equipment.

Ways of improving my experiment

• To make me results more accurate I could use more accurate equipment and make sure only the variables alter only (alcohols and water).

•  Keeping the distances exactly the same between the burner and the copper beaker. I could have use a sort of shield around the spirit burner and the copper beaker, which would have kept the heat from the burner directly concentrated on the copper baker giving a much more accurate reading.

• I could have tested more alcohols and different structure types e.g. (butanol isomer 2 and propanol structure 2) this would have given me a chance to see if any other alcohols are better or worse than the ones I have tested

•  I also could have tried altering the water levels this might have produced different results. I could also have investigated other factors that affect the heat of combustion such as length of the wick. These factor could all be written into or improved on in experiments to come

 

NOTE : The timing is incorporated into my experiment because I lost my results and I could only get one from another science group. Who used timing in their experiment)