The different alcohols that will be used are:
- ethanol
- propanol
- butanol
- pentanol
The variables that must be kept the same are:
- Mass of water - 50cm³
- Temperature rise of 30ºc
- Same starting temperature
The variable that needs to be changed is:
Diagram:
Prediction:
I think that the more bonds holding the carbon, oxygen and hydrogen atoms there are, the more energy will be released when the fuel is burned. Longer molecules require more energy to break their bonds because there are more bonds to break. So, for example, I can predict that hexanol will require more energy than ethanol because there are more bonds to break.
Results:
To calculate the average energy per gram we used the following equation:
Energy = Mass x 4.2 x change in temperature
Conclusion:
I have found from this experiment that my earlier prediction turned out to be correct. The more carbon atoms there are in the fuel, the more energy is required to break those bonds. It appears that my results were quite different to the textbook results for various reasons, however according to the textbook results, I had predicted correctly by saying that the more bonds holding the atoms, the more heat energy will be produced to break those bonds.
Evaluation:
There are many reasons why my results were so different to the original textbook results. The experiment could have been carried out in many different ways to prevent so much heat being lost to its surroundings. One way of reducing heat loss would have been to put heat mats around the experiment; however this is not the best way of preventing as much heat as possible from escaping.
It is a common scientific fact that all objects naturally absorb and emit heat so all the objects around the experiment such as beaker, work surface, etc. would have absorbed some of this heat. The fact that the alcohols all had different size wicks add to the fact that the flame may not always have been directly touching the bottom of the tin can therefore it would take slightly longer to heat up. It was very difficult to carry out a perfect experiment in a classroom because there are so many different ways of losing heat. Windows and doors may have been open making it even easier for heat to escape quickly. If there is a low oxygen supply, it is possible that some carbon atoms will be let out before getting a chance to bond with any oxygen atoms forming a substance called soot. To prevent this I would have to make sure there is a proper oxygen supply.
To improve this experiment I would simply try to carry it out under better conditions where as little heat will be lost as possible. This is one possible way of constructing the experiment :
If I managed to do the experiment this way I would think that the results would turn out similar to the textbook results.
