Lab 11B: Calories in Food

In this lab, we indirectly measured the amount of Calories per gram of three sample food items: a pecan, cashew, and cheese puff.  To do this, we used a calorimeter made of an Erlenmeyer flask filled with water on top of a metal can (which acted as a stove).  We ignited the food item, which was underneath the metal can, and measured the change in temperature of the water in the flask above.  By doing this, we were then able to calculate the amount of energy in the food tested because the heat gained by the water equals the heat lost by the food item.

A pecan burning in the calorimeter

Data Table and Calculations:

Questions:

1.  We measured a temperature change in the water.  The water absorbed the heat given off of the burning food, so we knew that the heat gained by the water would be equal to the heat released by the food sample.  Therefore, the temperature increase in the water is also the temperature change in the sample.

2.  We measured the energy released by the food sample, which is the same as the energy gained by the water, since the energy released heated the water.

3.  The small amount of energy that was not absorbed by the water could have escaped through the holes in the metal can as smoke and been released into the surrounding air.

4.  I was expecting the nuts to have more Calories per gram than the cheese puff because of previous knowledge, but it turned out to be the other way around.  This is most likely because our cheese puff didn't burn thoroughly and the mass of food burned was too small (0.04 g compared to 1.25 g and 1.38 g of nut burned).