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Practicals

Releasing Energy in Food
AKA: Food Burning

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Fig 1: Apparatus diagram
Fig 1
Fig 2

Summary

A sample of food is burnt to determine how much energy it contains.

Operation

Different foods contain different amounts of energy as we all know. This energy can be used to heat a boiling tube of water when burned. By recording the temperature increase in the water, we can work out how much energy the food contains.

Equipment required (per set):

  • Food samples (see below)
  • Boiling tubes
  • Clamp, boss and stand
  • Digital balance
  • Mounted needle for burning
  • Bunsen burner
  • Heat proof mat
  • Weighing boats

The foods to be tested can include:

  • Crisps
  • Pasta
  • Bread
  • Marshmallows
  • Cracker
  • Biscuits
  • Bacon etc

Each set should include about five or more samples so that a variation in results can be recorded.

A small sample of each food is firstly weighed on a digital balance. A boiling tube is filled with exactly 10cm3 of water and clamped firmly to a retort stand. The temperature of the water should be taken and recorded before being heated.

The food sample should be fixed to the very end of a mounted needle. These can be purchased through lab suppliers or can easily be made from a small piece of wooden dowel and a needle or piece of nichrome wire.

The food sample should be lit from a Bunsen burner and then held about 1cm below the boiling tube. If the flame goes out, it should be relit immediately. Once the food stops burning, the water should be stirred with the thermometer and the temperature recorded.

The experiment should be repeated using all the food samples.

The samples which heat the water to a higher temperature do so because they contain more energy. Higher ability groups may use the data to work out how many joules of energy the food contains and then compare that result with the packet data. If this is the case then you may need to keep the wrappers and packets that to food came in to back this up.

Safety

 Wear eye protectionWear eye protection.

Pupils should not taste foods.

The contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.