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Thermodynamics/Calculating food calories using Q=MxCxdeltaT

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Question
Hi,

My son is doing a calorimeter food science project for his 5th grade science fair.  We modeled a calorimeter to burn the samples and then used the calculation of Heat=Massx1cal/g celciusx(delta)T.

We burned half a serving size (14.1g) and heated 200ml (g) of water.  By multiplying the delta T by 200 and dividing by 1000 we get a very small Calorie figure.....5.44 Cal vs. 160 Cal!  We don't know why?

We will try to burn one chip, frito, cheeto, etc. and multiply up to the serving size but still, why wouldn't we get a Cal calculation closer to the bag's information by burning 1/2 a serving size and doubling it.

Any help on this would be great.  Thanks so much!

Michael Pray

Answer
I haven't used a calorimeter since my college days.  Did you take into account the heat gained by the calorimeter?  A bigger sample should give you a bigger temperature change and help with errors due to small temperature changes.  Certainly you should try several different products.  

Thermodynamics

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Richard J. Raridon

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