- Crucible
- Mineral wool
- Heat proof mat
- Timer
Method for Preliminary experiment
- Put 3ml of alcohol and a small amount of wool into a crucible.
- Light it
- As soon as the alcohol has lit start timer.
- Leave alcohol burning
- As soon as alcohols finishes burning, stop timer.
I will repeat this experiment four times; each time I do it I shall burn a different alcohol.
Preliminary Results
From looking at the table we can see that all the alcohols burn for 4:30 minutes or more, this means I shall therefore allow the alcohols to burn for fours minutes each in the experiment.
Main Experiment
Method
Equipment needed:
- Crucible
- Thermometer
- Mineral wool
- A empty can (i.e. a coca cola can)
- A clamp
- A boss
- Stand
- Heat proof mat
- Water measurer
- Timer
Here is a diagram to show hold my experiment will be set up:
- Once the experiment is set up.
- Put 3ml of alcohol and a small amount of wool in the crucible.
- Record the temperature of the water in the can.
- Light the alcohol in the crucible.
- Using tongs place the crucible under the can; at this point start the stopwatch.
- Allow the alcohol to burn for four minutes.
- After four minutes is up, using the thermometer take the temperature again of the water in the can, at this point also remove the crucible from beneath the can.
- Extinguish the flame by putting the crucible lid on the crucible.
For each alcohol; Methanol, Ethanol, Propanol and Butanol I shall repeat the experiment three times. I am doing each experiment three times so I can get the most accurate results possible by finding an average of the three results. In these averages I shall not include anomalous results, this is because they will not make the final result accurate as they may not be part of a pattern in my results.
Safety
To make my experiment safe I will wear safety goggles at all times and always stand up throughout my experiment.
Prediction
In this investigation I think that Butanol will give out the most heat energy as it has more bonds to break when combusting. I think methanol will give out the least heat energy as it has the least amount of bonds to break.
Here is a diagram showing the amount of bonds Butanol and Methanol have.
Methanol Butanol
Butanol clearly has more CH bonds than Methanol and so will give off more heat energy when breaking them therefore making it the best fuel.
I believe the alcohols will behave this way as this is the way Alkanes act when they combust.
Here is a graph that shows the order in which Alkenes combust. From looking at it we can see that Methane gives out the least heat energy as it has the least CH bonds and Hexane gives out the most energy as it has the most CH bonds. The rule for this graph is; the more bonds, the more energy given out.
Results
Here is a table to show the results I collected. This table shows I repeated the experiment three times, this was so I could work out an average of the results to get an accurate end result. It also shows the start temperature of the water, the finish temperature of the water and the temperature difference.
Averages
Here is a table to show the averages of the results. I have found the averages by adding up the three results then dividing the answer by three. I will not include anomalous results in my averages as it will make the final result inaccurate.
E.g. The average of Methanol’s start temperature:
/ = divided
20+20+22=62
62/3=20.6
Round up the number = 21
Calculating the amount of energy released
To calculate the amount of energy that each alcohol gives out I have to multiply the amount of water heated (60) by 4.2 and then multiply that answer by the rise in the temperature.
Therefore;
ENERGY (Joules) = Amount of water heated (ml) x 4.2(ml) x temperature rise (°C)
Multiply = *
Methanol
- 60 x 4.2 x 47
- = 11844
- Therefore 11844J were given out by Methanol.
Ethanol
- 60 x 4.2 x 49
- = 12348
- Therefore 12348J were given out by Ethanol.
Propanol
- 60 x 4.2 x 56
- = 14112
- Therefore 14112J were given out by Propanol.
Butanol
- 60 x 4.2 x 66
- = 16632
- Therefore 16632J were given out Butanol.
Here is a chart to show how much energy each alcohol gave out:
Chart A shows Methanol gave out the least energy and Butanol gave out the most energy. Starting from Methanol the alcohols gradually give out more energy finishing with Butanol giving out the most energy.
The following chart (below) shows that as the number of CH bonds increase the amount of energy given out increases also.
From looking at the above charts we can see that as the amount of CH bonds increases, the amount of energy given out increases. More energy is given out as there are more bonds to break. My results show that my prediction was correct and when alcohols are burned they do behave the same way as Alkenes and that Butanol is the best fuel and Methanol is the worst.
Evaluation
I believe that the results I collected when doing my experiment back up my conclusions very well.
Most of my results are fairly accurate as I did each experiment three times then found the average of the three results however; I have one anomalous result which I did not include in my averages.
I therefore believe that my results are sufficient enough to back up my conclusion which is that alcohols behave in a similar way as Alkenes when they burn in that as the number of CH they have increases the amount of energy they give out increases also. My results also prove that me prediction was correct.
However, if I were to do my experiment again I there are a few things I might change/do improve it:
- Use more alcohols to see if the pattern with the CH bonds continues.
- Repeat the experiment 5 or 6 times to get an even more accurate result
- Check the temperature of the water at regular intervals rather than at the start and the finish.
- Use more water so it did not heat up as fast.
- Record the weight before and after the alcohols have been burned and work out the alcohol on moles.
