Diagram
Method
- Collect and set up apparatus as shown in the diagram.
- Measure 20ml of water in the measuring cylinder.
- Pour into copper container.
- Place thermometer in the water and record the starting temperature.
- Weigh fuel container, record weight for before the experiment.
- Make sure all safety precautions are in place (safety goggles, heat proof mat).
- Ignite fuel containers wick.
- When there is temperature change that is noticeable then put out flame.
- Weigh the fuel container and record weight after experiment.
- Repeat 3 times for each fuel.
PREDICTION
I Predict that the more bonds there are holding the atoms together the more energy will be needed to break them up. So if there were more bonds holding oxygen, hydrogen and carbon there would have to be a certain amount of energy to break them apart, and so the water in the copper container would be heated faster.
For example a single bond of carbon and hydrogen has an energy value of 410 joules. It is this value that has to be overcome so it can be broken up. Ethanol has five of these bonds so you would have to multiply this number by five. The total number in joules is 3270.
I can predict that the longer the molecular structure the more energy would be needed to break them apart. I can say that Butanol would produce more energy then Methanol only because there are more to break in Butanol.
To also make this experiment slightly easier, I can calculate the bonds broken and the bonds formed, this being my theoretical results.
These are the energy figures that each bond has:
- C-H 412joules of energy
- C-O 743
- O=O 496
- O-H 463
- C-C 348
- C=O 743
What this is showing is that the reaction needs to have 413joules to separate the bond C-H. If all of the alcohols were added up the same way we would find the total number of joules to break the bonds. We know ethanol has five C-H bonds so if we times this by five we would get 2065 joules. So if we added up all of the alcohols in the same way we would know the amount of energy which to apply to it to break the bonds apart.
Bonds broken – bonds formed = calculation of energy change.
These are the results of the energy change of the reaction.
The formula for these reactions is:
Methanol CH3 OH CO2 + H2O- H
This is an example of complete combustion
Ethanol C2H5 OH CO + H2O - H
This is an example of incomplete combustion. This is when there isn’t as much oxygen present for the reaction to take place.
This reaction is anhamogoulous because the number of Hydrogen atoms increases by two in each formula.
All reactions need energy to overcome the activation energy. This is so the bonds can be broken and the reaction can take place. Once that has happened the reaction loses energy, if the energy drops past the original energy value then it is an exothermic reaction, although if the energy drops but is above the original value then it is a endothermic reaction, which feels cold.
These results are my average results and also on the right there are the actual results in joules. I will have to putt on a graph to see a pattern and any relationships.
As you can see series one in blue are my predicted results and the pink series are my actual results in joules. I ca notice that propanol is the main anomaly, although looking at the graph the both of the series don’t look more alike then not, so this go and prove what has been said. The more bonds that have to be broken the more amount of energy will be produced.
EVALUATION
What can be said about this experiment is that we could have lost a lot of energy while doing this experiment. Some of the heat could have been lost to our surroundings and so measurements and recordings could have been off. It might be an idea to have burnt our alcohol in pure oxygen to make sure that there was a complete reaction. An incomplete combustion is where there isn’t enough oxygen to release the energy.
By looking at my measurements and results there are a few anomalous results, which but nothing that is out of the ordinary. There could be a few anomalies because of the way the experiment was carried out; it does depend on how long the alcohols were burnt for. I measured it until there was a temperature change, so one might have been heated longer than others. This factor might have produced results that don’t seem to fit as well. Although by looking at the graph all of the figures seem to fit.
I found that the actual results were much lower than the theoretical ones. This could be because of some of the factors that I mentioned earlier about losing heat to surroundings areas and so on. Although I have to evidence to show this.
What is also very interesting is that calorific content in food would be very similar in the way of finding the energy and the energy produced in a piece of food. Most foods are measured in kilojoules for 100 grams, which is deceiving because we don’t usually eat 100 grams of food at a time.
