Temperature rise in oC * Volume of Water in cm3 * 0.0042 = Energy content in kJ
This gives you the amount of kJ per however much the food weighs but I want to find out how many kJ there are per 100g so I will do the following:
100/Weight Burned * Energy content = Amount of kJ per 100g
I will do this for all three tests and then find the average (All results added together divided by number of results). Then I will follow all of these tests for the other three foods.
Prediction
If I want to make a good and accurate prediction then I need to look at the composition of each food (e.g. amount sugars and proteins in it), to help me.
Note: All amounts are per 100g.
I think that the more proteins, fats, and carbohydrates the food contains the more energy it will be able to supply and thus the longer it will burn. I say this because fats are broken down into fatty acid molecules and glycerol molecules, proteins are broken down into amino acid molecules and carbohydrates are broken down into glucose molecules (these are broken down during the process of digestion they don’t just break down at random). All of these provide energy so, as said before, the more there are the more energy you get. So my prediction is that the sweetened banana chips will contain the most energy.
Calculations (using the equations previously listed):
Averages:
When going back to my original prediction it looks as if it was quite the wrong idea as, when looking at the results, one can see that the sweetened banana chips do not contain the most energy, as I thought, instead the salted peanuts do. Following is a table of the energy contents that were listed on the packets:
As can be seen a comparison between the energy contents listed on the packets and the results from the experiment there is a significant difference. When my original prediction is compared to the energy contents listed on the packets it looks almost as if my prediction was still quite far off, here, the sweetened banana chips contain the third greatest amount of energy.
Evaluation
As can be seen by comparisons between actual energy contents and results I got, the experiment was probably not very accurate, though this is not because the experiment was done wrongly. There were so many things that could not be helped in the experiment. A large amount of heat was lost in the form of heat. Heat was absorbed by the surrounding air, energy was lost during the transition of the burning food from the candle to the test tube. Another source of heat loss was the test tube itself. The test tube was heating up as well as the water and heat was escaping form it into the air. Another factor was that there were probably plenty of air currents flowing through the room both warm and cold, warm from other peoples candles and cold from the outside air. These air currents probably affected the temperatures of the water and the flame of the burning food in quite a big way. Another factor is the oil, grease and fat that dripped off of the food as it burned, these drops would have been enough energy to keep the food burning for a while longer than it would actually have done. I would say that all of these uncontrollable variables were what affected my results, making them as low as they were.
Despite the fact that my results may not exactly have been superbly accurate, they are still reliable enough to base a firm conclusion on. I can tell from my results that the salted peanuts contained the most energy, probably because of the salt on them, which I did not take into account when I was making my predictions. I can also tell that the ones with a smaller energy content were the original flavour Hula Hoops and the toffee popcorn.
To improve my method and increase the reliability and accuracy of my results there are a few things that I would have done. Primarily I would have tried to decrease the amount of oil that dropped off of the burning food, possibly by putting the food on a ceramic tile instead of on a spike so that any oil would still be burnt. Another thing I would have tried to change is the method of setting the food alight, since so much energy was lost that way.
Another experiment that could be performed to more accurately discover the energy contents of different foods is the same experiment that is used to oxidize sugar. The setup of apparatus is shown below:
This experiment would be far more accurate for quite a few reasons. First of all no real amount of energy is lost through the air as the burning sugar is surrounded by the water that it is supposed to be heating up. No heat is lost through the heating of the test tube (or in this case the jar or beaker which contains the sugar) because although it is heated, the heat only serves to heat up the water even more. No energy is lost during a transition of the lighted food to the jar as it is lighted in the jar. The hot gases that rose off of the food while it was burning was wasted during my experiment but for this experiment it heats the water as it rises since the tube which it rises through is also surrounded by water. So, overall this experiment is a far more accurate way of measuring the energy content of foods.
