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Analysis and Conclusion
Which alcohol gives off the most heat when burning?
My hypothesis was:
There is a direct proportion between the size of the alcohol and the amount of heat produced by burning 1 mole.
When looking at the graphs that I produced it is clear then graph one shows a clear trendline, where as graph two showed one but not as obviously. Graph three is an average between the two.
There is clearly a relationship between the carbon number in alcohol and the energy per mole of alcohol as the average of two results produced a curve graph.
If I do not use the results obtained for graph 2, and only take in consideration those of graph 1, then clearly the directly proportional relationship which is clear will be supporting my hypothesis; as the alcohol becomes stronger, the energy per mole of alcohol also increases proportionally.
This is due to the collision theory. Since there are more carbon atoms in each alcohol as the strength of the alcohol increases, there is an increase in surface area, as the alcohol becomes stronger. So when there is an increase in surface area is decreases the amount of collisions and collisions occur on the surface.
Looking at my graph you can see that there is a lot of scatter, not all the points are plotted on the line of best fit exactly.
There could be many reasons for this scatter.
The reason for this could be the fact that the boiling tube is an insulator, therefore it keeps the water at its same temperature for a longer period of time before cooling and when it does cool it will cool slower.
Another reason is that there is a significant amount of heat escaping from the flame before reaching the boiling tube, as the boiling tube is not held directly above.
Also there was a slight draft, increasing the heat loss of the flame. As the flame is closer to the water in the top of the tube, the water at the bottom is cooler. When the thermometer was placed in each time to read the temperature I just randomly placed it in the water not thinking about whether I was measuring the temperature of the water at the top or at the bottom.
Before beginning the experiment we had to soak the string in the alcohol and make sure it had all soaked up alcohol. When we soaked the stem we placed it in the alcohol for around a few minutes began the experiment.
I knew however that it had not completely soaked as it burnt, which would have effected my results.
All of the things I have mentioned contributed to the large scatter and anomalous results. Although some of the points are unable to be changed there are a few ways to get more reliable and accurate results.
· Mark on the thermometer where the water reaches when it id put in the water so that it always measures the same part of the water.
· Insulate the boiling tube with a material such as wool so that heat does not escape.
· Set a certain time for the string to burn for, for example 5 mins, making sure it is fully absorbed.
· Cover the flame with something such as foil to prevent any other heat loss but to make sure the flame stays lit a hole must be made.
To make my results even more reliable and I could have taken more readings, as this would have allowed me to draw a better and more reliable graph, as I would have more plots to draw. I could have also done three trials or even four and taken the average from there.
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Chemistry, Physics, Matter, Heat transfer, Temperature, Thermodynamics, State functions, Oxides, Ethanol, Properties of water, Heat, Thermodynamic temperature
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