I'm an absolute beginner in chemistry.

How do I measure the energy density of fat?

As a specific example, I'd like to verify that 1 gramm of fat has 37 kilojoules.

I guess that measuring the energy density involves burning that fat.

  • $\begingroup$ What type of food are talking ab . . . Actually, that doesn't matter. Since food isn't just fat, this gets way too broad, even for just a specific type of food. You'd never get accurate enough. $\endgroup$ – M.A.R. Aug 7 '17 at 16:48
  • $\begingroup$ Burn it! Calorimetry. $\endgroup$ – a-cyclohexane-molecule Aug 7 '17 at 16:53
  • $\begingroup$ Thanks for your comments! @M.A.R. If we never get accurate enough, where do the figures on the nutrition labels come from? $\endgroup$ – Matthias Braun Aug 7 '17 at 17:09
  • $\begingroup$ Hi @MatthiasBraun, the determination of caloric content, in the US at least, is briefly discussed in the article below. The accuracy of the measurement is dependent on the sensitivity and and quality of the instruments used. If you perform this measurement with common items, the accuracy will suffer due to sources of error. scientificamerican.com/article/how-do-food-manufacturers $\endgroup$ – J. Ari Aug 7 '17 at 17:13

You are correct that you would need to burn the sample, in your case a fat. The basic approach is to burn the sample in an apparatus that will cause the heat generated in the reaction to warm up a known quantity of water. The temperature change of the water is measured, and with a known mass of water and the water's heat capacity, you can calculate the amount of heat energy that was generated from burning your fat sample.

Here is an example procedure of how to conduct a basic calorimetry experiment to determine the energy content of a sample of food and the equation that is used to calculate the energy content. Note, however, that this method is very rudimentary and will not guarantee a high degree of accuracy.


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