Science Buddies: "Ask an Expert"

Hi! I am doing the Burning Calories: How Much Energy is Stored in Different Types of Food? experiment and have done the experimental procedures and am now ready to calculate the results. However, the formula Qwater = mcΔT (which was included in the intructions) does not use the information about the initial and final weight of the burned items. I need to calculate the energy released per unit weight of each of the food items and the average values for each food type. I was just wondering if there was a formula I need to use to get that information. If someone could help me that would be fantastic. Thanks!

Hi!
Reading the sciencebuddies guide, it seems that you can simply divide the Qwater (amount of calories) by your weight to find out that calories per unit weight. be sure to measure the weight in grams as well. Hope this helps, good luck!

Hi Dragonese,

I think you are looking at this science buddies project:

https://www.sciencebuddies.org/science- ... p013.shtml

I think the example given, helps with the question you are asking about the calculation.

Qwater is the heat captured in calories, and the answer you want. This is equal to:

(the mass of the water in your calorimeter in grams) x (the specific heat capacity of water, which is 1 cal/g degrees Centigrade) x (the change in temperature you have recorded in degrees Centigrade).

Since the specific heat capacity of water is 1, you just need to multiply the weight of water in your calorimeter (in grams) x the change in temperature (in degrees Centigrade), and you will have your answer.

Does this help? Let us know if you still need help.

Donna Hardy

Dear dragonese101,

I understand your confusion since it seems that weighing after it has burned is not necessary. It seems to me that to find out the number of Calories in each type of food, you use the equation Qwater = mcΔT and divide that result by the number of grams since it says "the energy per unit weight of each food item (in calories/gram and Calories/gram)." I think grams must be the initial weight of the food.

Good Luck!

Hi Dragonese101,

Michele is correct. The equation you asked about, and that I explained above, just gives you the total number of calories in the food. If you divide this number by the weight (in grams) of the food item you burned, you will have calories/gram of food.

Donna Hardy

Thank you sooo much that really helped me a lot!