Energy in Food

Question 1

What experiment involves burning food, to see how much energy it contains?

Answer 1

1) Weigh a small amount of dry food and then skewer it on a mounted needle.
2) Add a set volume of water to a boiling tube (held with a clamp) - this will be used to measure the amount of energy that’s transferred when the food is burnt. You can insulate the tube with foil to minimise energy loss to surroundings.
3) Measure the temp. of the water, then set fire to the food. Make sure the Bunsen burner is not near the water.
4) Immediately hold the burning food under the boiling tube until it goes out. Then relight the food and hold it under the tube - repeat this until the food won’t catch fire again.
5) Measure the temperature of the water again.

Question 2

What is the formula for energy in food?

Answer 2

Energy in Food (J) = Mass of water (g) x Temperature change of water (°C) x 4.2

Question 3

What is the formula for energy per gram of food?

Answer 3

Energy per gram of food (J/g) = Energy in food (J) ÷ Mass of food (g)