To investigate the energy content of different foods.

   The number of calories needed each day depends upon how much energy an individual's body uses. An active child can need more calories than an adult who works at a desk. The body needs more calories in cold weather to stay at an even temperature.  

Prediction/Hypothesis: I think that the Brazil nut will contain the most energy. I did some energy amounts each food has, the results are as below;

                Brazil Nut: 265000 joules per gram  

                Peanut: 24600 joules per gram  

                Bread: 24600 joules per gram  

                Pasta: 2500 joules per gram

Although both types of nut contain high levels of energy, they might contain less of other substances, like protein, for example. Which Bread and Pasta can provide more of.

Diagram:                                                                  

Method:

        1) Set up apparatus as shown in diagram

        2) Weigh all of the foods

        3) Make a note of the temperature of the water in the test tube.

        4) Light the food (this may take some time with the pasta) with a bunsen burner.         Remember to keep this flame away from the test tube.

        5) Move the food directly under the test tube.

        6) Wait until the food has completely gone out.

        7) Record the temperature of the water in the test tube immediately after the food has gone         out.

Results:

Food        Experiment 1                Experiment 2                

(Weight)        Start        Finish        Start        Finish

(grams)        Temperature (degrees Celsius)                                

Pasta        23        40        18        57

(1.54)                                

Peanut        21        50        24        86

(1.56)                                

Bread        27        37        20        43

(0.33)                                

Brazil nut        22        76        19        91

(0.46)                                

I use the following formula to calculate the amount of energy in the food;

Volume of water × temperature / mass of food

                Brazil nut: 13695 joules per gram  

                Peanut: 2916 joules per gram  

                Bread: 4999 joules per gram  

                Pasta: 1817 joules per gram  

Conclusion: As I predicted, the Brazil nut contained the most energy, they were followed, suprisingly, by bread (this was probibly due to an error in my method, this is discussed in my evaluation. The Brazil nuts contained the most energy because of many reasons in it's chemical make up, but, even though they are high in energy, they might be lower in minerals, fibre and calcium as other foods.

Evaluation: There are a number of things that could have affected the outcome of the experiment, they are as follows:

a) There was a problem with getting the food samples to stay on the pin. During the time when I was replacing the food, some of the heat energy that would have been transferred into the water in the test tube would gone into the air, reducing the total amount of heat energy transferred into the Water.

b) Some of the heat energy produced by the food went either through the pin, into the air or into the glass of the test tube.

c) When lighting the food, some of the heat energy from the bunsen burner would have gone to heat up the water in the test tube.

d) I could have inaccurately read the scale of the thermometer, although this wouldn’t have mattered if I made the same inaccuracy all the time.