The bread is expected to burn the least unassisted, the cracker the most, with the cereal in between the two values. This prediction is based on the chemical construction of the foods. The cracker has the least amount of air-pockets, contributing to the assumption that it will engulf in the flame with more ease.
Procedure:
- Set the equipment up to have the same configuration as figures 1.1 and 1.2 on the next page.
- Fill a 25mL graduated cylinder with water, ensure that the meniscus is at the highest graduated marking.
- Place the calorimeter on the centigram balance and record the mass in the data table. Slowly add water into the calorimeter until you reach a desired whole number. Record the total mass and the mass of just the water into the data table.
- Place a thermometer into the calorimeter and after three minutes record the result as the initial temperature.
- Break off a piece of the food to be tested, weight and record it.
- Place the calorimeter onto the top level of the stature made by the stand and clamps (with the thermometer inside).
- Hold the piece of food with the tongs. Slide the user-end part of the tongs down the index finger and thumb towards the hand. Using the other hand and the thumb and index fingers from the hand holding the tong, light a match. Hold the match underneath the piece of food until it ignites.
- When the piece of food ignites, move it underneath the wire gauze holding the calorimeter. Should the fire go out, relight a match and subsequently the piece of food as depicted in step seven.
- Burn the piece of food down to the ashes remaining. There would be left a chunk. Put this chuck on the centigram and on the datasheet collect how much food was burnt.
-
Three minutes after the conclusion of the trial, read the temperature and record .
(Continued on next page)
- Repeat steps 2-10 for the rest of the trials (there should now be eight trials left to make a total of nine).
- Using the equations from the next page, calculate the amount of Heat Calories the food emits and the energy yield.
Materials and Equipment:
- 1 – Calorimeter (Dole™ Juice Can)
- 1 – Graduated cylinder (25mL)
- 1 – Thermometer
- 1 – Centigram balance
- 1 – Set of stands and clamps
- 2 – Firm wire gauzes
- 3 – Packets of matches
- 1 – Pair of Tongs
- 4 – Crackers
- 1 – Slices of Bread (White)
- 4 – Bits of Cereal
- ±170mL of Tap Water
References
Data Analysis
For the energy yield below, the accepted values are calculated to the mass of the food tested in the experiment.
Graph created using Microsoft Office Excel 2007 Application
In the graph above, the accepted values of the Energy Yield are presented with the experimental value taken by the researcher in the darker colour and the accepted value from a credited resource in the lighter colour. In the data collected versus the data accepted, the errors in the values were 87%, 67%, and 89% respective to the bread, cereal, and crackers.
Sources of Error/Improvements
The most prominent source of error in the lab was the amount of relighting that occurred. The food had to be relit, as predicted in the hypothesis, yet on a much greater scale. The amount of heat and energy lost while relighting the food was not dire but did affect the outcome, nonetheless. However, the continuity of the burns was affected in the sense that not all of the trials were given the same amount of time to burn. Early on into the experiment, an error was recorded about the placement of the thermometer in the set-up of the calorimeter. The sensor (bulb) was placed against the metal and therefore recorded a higher temperature than it would have otherwise. This error, however, counters another error which the researcher experienced. Since there were many metal parts, including the wire gauze underneath the calorimeter, the heat was dispensed and there was a great deal lost. With the sensor placed against the bottom of the calorimeter, this compensated for some of the heat lost during the trial.
As not to ruin the continuity of the experiment, these improvements were not implemented but developed. As to not vary the difference in the energy lost while relighting the experimental food, the food could have been placed directly underneath the calorimeter and fixated to be lit from there. The reconstruction of the experiment would include the calorimeter to be hung from a string or wire as not to have heat lost of metal clamps and gauzes. The thermometer would therefore be placed into the water, not touching the sides or bottom of the calorimeter and read the direct, more exact value.
Conclusion
Through the interpretation of the data, it is evident that not only was there a big difference in the values (experimental vs. accepted), there was a big difference in the method of getting the resultant Energy Yield. In the experiment, the researcher was burning food and finished with the heat calories. This is not exactly how the body ingests and breaks down food. In this sense, with the factors involved, the experiment is more or less successful due to the fact that there were values that were obtained and could be validly interpreted by the researcher.
For the bread tested, the accepted value was seven times the amount of the value of the experimental. For the cereal and crackers, the accepted value was three times and nine times larger, respectively, than the value calculated with the experiment. However, even with the difference in the values, the trend predicted in the hypothesis occurred. The bread had the least amount of energy yield, the cereal had slightly more, and the cracker had much more.
In addition, the time required for burning was relatively similar to that predicted in the hypothesis. The cracker had to burn for a long period of time and had to be relit few times. The bread needed to be reignited many times and burnt for a short period of time in general.
Resources Used
Accepted Values for Foods:
New York Times Company. Calories in Bread. 26 November 2008
<http://caloriecount.about.com/calories-bread-ic1802>.
New York Times Company. Calories in Breakfast Cereals. 26 November 2008
<http://caloriecount.about.com/calories-breakfast-cereals-ic0800>.
New York Times Company. Calories in Crackers. 26 November 2008
<http://caloriecount.about.com/calories-crackers-ic1805>.
