2.32 describe an experiment to investigate the energy content in a food sample.

Finding the amount of energy in food

This is also called calorimetry.

Experiment

1. Obtain a dry food sample that will burn easily
2. Weigh the food and skewer it on a needle
3. Add 25cm3 of water to a boiling tube
4. Measure the temperature of the water
5. Light a bunsen away from the water
6. Put the food in the bunsen burner and then place the lit food under the test tube. 
7. Once the foods gone out relight it and repeat this until the food will not light again.
8. Measure the final temperature of the water

Calculations:

To find the energy in Joules:

Energy in Food (J) = Mass of Water (g) x Temperature Change (C) x 4.2

• The mass of the water is the same as the volume (1g of water = 1cm3 of water)
• The 4.2 is the Specific Heat Capacity of Water. You will have learnt about this in Chemistry but it just is the amount of energy needed to raise 1g of water by 1 degree.

To find the energy per gram:

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

NB - This means you can compare food stuffs fairly.

To increase the accuracy

• Insulate the boiling tube with foil to reduce heat loss would improve accuracy
• Use a calorimeter will improve the accuracy of your results.