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# Find the relationship between amount of fat and amount of energy produced in different foods.

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Introduction

July 2001 Biology Coursework Year 10 Aim Find the relationship between amount of fat and amount of energy produced in different foods. Planning I am going to ignite different foods and see how much heat energy they give out. The food that causes the biggest amount of change in temperature will have the most amount of energy. However, calculations have to be carried out to create an average energy output per gram. Variables Independent Variables: This will change from food to food, thus giving me a range of different results. In this experiment it will be type of food. Dependant Variable: This is the amount of Energy per gram which can be calculated Controlled Variables: These are the things that will keep the same, in order to sustain a fair test. These are; * Apparatus * Type of boiling tube * Distance of boiling tube from Bunsen burner * Distance of food from boiling tube * Amount of time taken to move ignited food to boiling tube Fair Test It is essential that I keep it a fair test in order to sustain accurate results for comparison at the end. To ensure a fair test, I must keep the controlled variables for every test I do. The apparatus must all be kept the same because there may be some minor differences in insulation properties, or measure of accuracy between them. If this were to happen, it would prevent me from sustaining accurate results. The same type of boiling tube must be kept constant because, every boiling tube may have different conducting properties. If it were not as dense as a previous test tube, it would heat up more quickly, and if it were denser, I would get the opposite affect. This is why it is essential that all the boiling tubes are identical as it could lead to totally false results. The boiling tube must be changed for each test though, because a previous boiling tube may have retained heat from a previous experiment. ...read more.

Middle

ENERGY (J/g) PUMPKIN SEEDS 0.1g 16?C 35?C 19?C 20g 1596 15960 0.1g 18?C 48?C 30?C 20g 2520 25200 0.1g 26?C 29?C 3?C 20g 1260 12600 CRISPBREAD 1.1g 15?C 25?C 10?C 20g 840 764 1.2g 16?C 32?C 32?C 20g 1344 1120 1.1g 17?C 29?C 12?C 20g 1008 916 1.1g 19?C 37?C 18?C 20g 1512 1375 Calculations Energy (Joules) = 4.2 x temperature difference x weight of water Energy (Joules/g) = Energy (J) Weight of food Crispbread 1. Energy (J) = 4.2 x 10?C x 20g = 840J Energy (J/g) = 840J / 1.1g = 764J/g 2. Energy (J) = 4.2 x 32?C x 20g = 1344J Energy (J/g) = 1344J / 1.2g = 1120J/g 3. Energy (J) = 4.2 x 12?C x 20g = 1008J Energy (J/g) = 1008 / 1.2g = 916J/g 4. Energy (J) = 4.2 x 18?C x 20g = 1512J Energy (J/g) = 1512 / 1.1 = 1375 Pumpkin Seeds 1. Energy (J) = 4.2 x 19?C x 20g = 1596J Energy (J/g) = 432J / 0.1g = 15960J/g 2. Energy (J) = 4.2 x 30?C x 20g = 2520J Energy (J/g) = 480 / 0.1g = 25200J/g 3. Energy (J) = 4.2 x 20?C x 20g = 1680J Energy (J/g) = 432J / 0.2g = 840J/g 4. Energy (J) = 4.2 x 3?C x 20g = 1260J Energy (J/g) = 480 / 0.1g = 12600J/g Results from Main Experiment FOOD WEIGHT OF FOOD START TEMPERATURE END TEMPERATURE TEMPERATURE DIFFERENCE WEIGHT OF WATER ENERGY (J) ENERGY (J/g) DRIED PEAS 0.49g 22?C 29?C 7?C 20g 582 1200 0.25g 23?C 26?C 3?C 20g 252 1008 SUNFLOWER SEED 0.13g 24?C 34?C 10?C 20g 840 6462 0.15g 21?C 26?C 5?C 20g 420 2800 PASTA 0.33g 22?C 24?C 2?C 20g 168 509 0.30g 24?C 26?C 2?C 20g 168 560 CRISP 1.48g 20?C 33?C 13?C 20g 1092 738 0.86g 24?C 37?C 13?C 20g 1092 1270 Calculations Energy (Joules) ...read more.

Conclusion

This could have been faulty equipment being used. The time taken for the food to be put under the boiling tube once lit was not measured. Therefore I suspect that it was different for every experiment. We did not time it and it was hard to tell when the food was totally ignited. This made the test unfair. Also there was the fact that not all of the energy was being used to heat the water. Some would have been lost. Also, the food is not completely burned. The black residue left behind proves this. Therefore, not all of the energy is used. I don't think there are many ways of improving the accuracy of the experiment large deal. If it were repeated around 5 times for each food, it may prove better because only two comparisons is not very helpful. When an anomaly was present, I often did not know which one was the anomaly, and had to find out via comparison with other pupils' results. Also, a larger range of foods should be tested. Therefore, there would be more means of comparison. The main cause of inaccuracy was the lack of energy reaching the water. To increase this, maybe if the burning food was placed into a metallic container, and the rise in temperature in the atmosphere in the container was recorded, it may be more accurate. However, one way to encourage the complete combustion is to burn the food in a higher concentration of oxygen than normal atmospheric conditions. However, oxygen is pretty explosive so it would require greater safety features and would be done in a controlled environment. That is why experimenting it in a bomb calorimeter, would be most accurate and is how official results are obtained. Bomb calorimeters burn the food in special chamber totally enclosed by the water it is heating. In these the food is burned in pure oxygen as this helps to ensure that it is totally burned and therefore all the energy is released. The experiment that we carried out is an example of a simple calorimeter. ...read more.

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A good account of the investigation including detailed discussion of unexpected results. There are too many incorrect references to energy being produced or created.

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Marked by teacher Adam Roberts 25/10/2014

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