Energy in Food

Food can be burnt to see how much energy it contains - calorimetry

Food scientists use machines called calorimeters to measure the energy content of our food - they’re insulated and sealed so produce much more accurate results than the simple experiment below.

1. You need food that’ll burn easily (something dry like dried beans or pasta)

2. Weigh a small amount of the food and then skewer it on a mounted needle

3. Next, add a set volume of water to a boiling tube (held with a clamp) - this’ll be used to measure the amount of energy it has transferred when the food is burnt

4. Measure the temperature of the water, then set fire to the food using a Bunsen Burner flame. Make sure the Bunsen isn’t near the water or it may affect your results.

5. Immediately hold the burning food under the boiling tube until it goes out. Then relight the food and hold it under the tube - keep doing this until the food won’t catch fire again

6. The last thing to do is measure the temperature of the water again.

Calculate the amount of energy in the food

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

1cm³ = 1g

2. Then work out how many joules are in each gram of the food. Compare the energy values of different foods fairly using the equation below.

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