Isomers Lab Report

The findings of this experiment indicate the hypothesis to be partially correct and partially incorrect. As was predicted, the experimental results did support the concept that as the carbon number increased so would the energy level. When comparing the energy levels of other isomers to straight chain alcohols, the graph shows the first part of the trend line for the other isomers to have a higher energy, while the less steep trend gradient means this switches over between 3 and 4 carbon, indicating that isomers with a carbon atom number greater than that will have increasingly lower enthalpy levels.

This variance in results when performed under near identical experimental conditions, suggests that energy produced during the combustion reactions
of alcohols, or fuels, can substantially vary. A possible explanation for this could be

This is inconsistent when compared to other previous findings which show that the values for other isomers should be higher due to…. Take ….. as an example….. Compared to this experiment individual point/set … Results… Comparitively the results average around 35%

This difference in results is likely to be due to flaws in the experimental process.
One key one was the data sample size, which was restricted by limited resources and time constraints. While five straight chain alcohols were tested over a spread of carbon chain lengths, only three other isomers chain length variants were available for use, which were all in a row. This meant that anomalies and individuals results would have had a larger impact on the trend line, and the results were a lot less accurate than the straight chain as individual results had a larger impact as the sample was smaller. Saying this, by repeating each variable three times the results were more accurate than if just tested once, but in general the experiments showed a fairly large difference between specific tests for the same variable. This meant that results weighed down a particular end of the spectrum, had a larger impact on of the averages that were used for calculations. Due to this variance, to get a credible result a large number of tests should ideally be
done.

Another key component was the efficiency of the calorimeter.
When comparing the predicted theoretical values to those achieved in this experiment, a 35% efficiency was achieved overall. This suggests that while the insulation worked to some extent, it was not as high as it could have been. Achieving an efficiency that is as high as possible is important to maximise the amount of energy transferred into the water (or alternate substance which the temperature difference is being measured), meaning that less heat escapes. While the hood worked well, there are several ways it could be improved. Firstly, would be to have the bottom of the hood lower down, so it completely covered the top of the shrowd meaning more of the hot air which rises will be pushed up towards the water barrel and there will be less lost into the environment. Secondly would be to increase the surface area of the barrel touching the hot air by having a narrow skinnier barrel. Thirdly, by using a retort stand with rubber clamps to hold the drum above the flame instead of sitting it on a tripod stand, loss of heat into the tripod instead of the water would be
reduced.

Further alternatives would be to change the whole design of the calorimeter. One idea would be to use a large container, filled with water, with a high Specific Heating Capacity with insulation around it, and coiling a narrow hollow tube made of aluminium or an alternate material with a low Specific Heating Capacity inside the container, with the bottom opening on to an inverted cone also made of a material with a low Specific Heating Capacity to maximise the amount of heat transferred to the water by easily absorbing it. By extending a hood out from the cone inside the container to just below the flame made of a high Specific Heating Capacity, increased amounts of heat is caught and sent up through the coiled tubes, and not into the surrounds or into the hood itself. By then using a lid on the top of the container, with a hole where the tubing is ran through, any carbon dioxide can still escape through so the flame is not choked and smothered. This maximises the amount of surface area where the heat can transfer into the water, minimises heat loss and then further promotes convection currents by ensuring the hot air moves, by tunnelling it through on a gradual basis using the principle hot air rises.

With these in mind, comparatively both the results of this experiment and others show the difference between straight chain and other alcohol isomers to be minimal. While the isomers may possibly give off higher energy levels when burnt, the question is whether the difference is substantial enough to be justifiable to favour other isomers over straight chain alcohols in industrial usage. Another thing to consider is the economical side of using other isomers, like branched chain, as they often require more complex reactions to produce those isomers, which are often more costly, meaning the increased energy levels could not be worth the extra cost. Others factors such as the cleanliness of fuels in terms of environmental impact and the reactants released when used are also important factors to consider in deciding whether straight chain or other alcohol isomers are more beneficial to use in industry as an alternative fuel, and is something that should be tested further in the future.
Conclusion
With current fuels set to run out in coming years, this report explored the idea of using alcohols as an alternative fuel, and tested whether using isomers other than straight chain released more energy in the combustion reaction, which is more desirable to increase the amount of bang for your buck. The hypothesis that isomers would have a higher energy of combustion level was not fully supported in the findings, that supported the hypothesis for alcohols with three or less carbons, but showed a lower energy level for any alcohols with any greater carbon number. This was different to what predicted values showed, the difference possibly justified by the limited number of tests. Overall other isomers were concluded to have a marginally higher energy level, but when considering economics and environmental issues, it was questionable whether the higher energy of combustion of other isomers than straight chains was significant enough to justify using isomers as a preferred fuel.