Methanol Pentanol
Each C-H bond has a bond energy of around 412Kj, because Pentanol has 12 C-H bonds where as Methanol only has 4, shows that Pentanol will give off more energy than Methanol when heated.
The five different alcohols I’m going to use are:
- Methanol
- Ethanol
- Propanol
- Butanol
- Pentanol
I’m going to test each alcohol three times to try and eliminate any mistakes that would lead to anomalies in the results. I will record the water temperature at the beginning and the end of each two minute experiment, I will also measure the mass of the alcohol at the beginning and the end of each experiment as well.
For this experiment to be a fair test I will make sure the following are kept the same in each experiment:
- Volume of water
- Mass of alcohol
- Starting temperature of water
- Distance between flame and metal can
As preliminary work earlier I investigated the amount of energy in different foods, this investigation used the same basic method as the one used in this investigation. The results were not very reliable and there were many anomalies in the results. Hopefully this investigation will provide more valid results.
Whilst obtaining the evidence I took the following precautions:
- Tucked tie into shirt
- Wore safety goggles
- Didn’t sit down at the table
- Waited for objects to cool down before I handled them
Results:
Working Out Energy Values:
I will use the following formula to work out the energy of each alcohol:
Energy (J) = Mass of Water x Specific Heat Capacity x Temperature Rise
I have drawn a line of best fit to show the basic trend of the results.
The evidence suggests that Pentanol gave off the most energy with Ethanol giving off the least.
The basic trend shown by this graph is proportional to the prediction I made earlier, as the amount of Carbons in the atom increase so does the energy released when heated. There is one anomaly that has shown up in this graph there could be many reasons for this:
- Miscalculation
- Distance between flame and can
- Volume of Water
- Misreading of the thermometer
- Wrong Alcohol used by mistake
The evidence shows that Pentanol gave off the most energy as it has the most Carbons, each C-H bond has an energy value of 412kj, as Pentanol has 12 of these bonds the total energy given off should be 4944Kj compared with Methanol with four C-H bonds that should have a total of 1648Kj. The is a big difference explaining the difference in this investigation.
The procedure is used was safe and successful and produced good results.
The quality of the results was fine as there was one anomaly. There are many reasons why this could have happened, as the method was not very accurate some heat would have been lost t the air and the metal can. If I had positioned the can too far away from the flame the results would not be accurate, this could be a reason for the anomaly.
The graph shows a strong positive correlation proving that my prediction was correct and the more carbons the more energy is released.
For more accurate results the experiment could be held in room of constant temperature. Equipment could be used to reduce the amount of heat lost to the surrounding air.
