Technically speaking, calorimetry is the measure of heat transfer, but measuring calories is also a way to find out how much energy a food item contains. When food is burned it releases a certain amount of its energy as heat. We can measure that heat energy by transferring it into a predetermined volume of water and seeing how much the temperature of the water rises. The amount of energy needed to raise one gram of water by one degree Celsius is known as a calorie. Therefore, if we burn a food item under a metal container of water, we should be able to determine how many calories were in the food item based on the temperature change.
Determining Calories in a Food Item
- Food items to test
- Large coffee can, with top and bottom removed
- Soda can
- Metal coathanger
- Metal pin
- Metric scale
- Centigrade thermometer
- Graduated cylinder
The temperature change may be easier to see using 50 ml of water. If you decide to use less water, simply adjust the formula at the end.
Always be careful when lighting anything on fire.
Push the pin through the length of the cork. If your pin doesn't pass through the cork and come out the top by about half an inch, simply push the pin into the side of the cork at an angle so it comes out one end. This is what you will use to hold your burning food in place.
Drill two holes in the sides of each can near the top so that you can see through both cans when all four holes are aligned.
Take a food sample, record its mass in grams and place it on the food holder.
Measure out 100 ml of water using the graduated cylinder and pour it into the soda can. Take the starting temperature of the water. Slip the metal rod of the coathanger through the holes in the coffee can and the soda can so that the soda can is suspended in air.
Stick the food item to be burned on the pin and place the food holder on a non-flammable surface, away from anything incendiary. Light the food item on fire.
Once the food is burning, immediately place the coffee can apparatus over the food holder.
After the food item has completely burned, carefully stir the soda can water with the thermometer and take the final temperature. (Both cans will be hot!).
Determine the calories in the food item using the following formula: Calories = mass of water (100 g) x change in temperature.
Things You'll Need
- The temperature change may be easier to see using 50 ml of water. If you decide to use less water, simply adjust the formula at the end.
- Always be careful when lighting anything on fire.
About the Author
Brett Smith is a science journalist based in Buffalo, N.Y. A graduate of the State University of New York - Buffalo, he has more than seven years of experience working in a professional laboratory setting.
Ingram Publishing/Ingram Publishing/Getty Images