Energy in Food

Question 1

How can you measure the amount of energy in a food sample? - Experiment

Answer 1

1. Weigh a solid food sample, then skewer it on a mounted needle.
2. Add a set volume of water to a boiling tube, and attach the tube to a clamp.
3. Use a thermometer to measure the temperature of the water, before burning the food sample with a Bunsen burner flame.
4. Immediately hold the sample under the boiling tube until it goes out. Relight it and repeat until it will no longer catch fire.
5. Finally, measure the temperature of the water for a second time.

Question 2

How can you measure the amount of energy in a food sample? - Calculation

Answer 2

1. Use the formula “Energy (J) = Mass of water (g) x Temperature change of water (degrees Celsius) x 4.2
2. Note that:
   a) 1cm^3 of water = 1g of water
   b) 4.2 is the specific heat capacity of water - the amount of energy (in joules) required to raise the temperature of 1g of water by 1 degree Celsius

Question 3

How can the accuracy of this experiment be increased?

Answer 3

Insulating the boiling tube (e.g. with foil) would minimise heat loss and keep more energy in the water - making the results more accurate.