Investigating Calories in an Apple

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Alexander Zouev

Physics IB HL 7/05/06

Umbrella topic
: Heat.  Subtopic: Heat and an Apple

Physics Lab: Investigating Calories in an Apple


        To measure the amount of Calories in a fresh average-sized apple, a dry apple ringlet, and an oven-dried apple ringlet using a Calorimeter.


        All foods including apples have energy within them.  Our human bodies can convert this stored energy that’s found in the foods (calories) and convert it into chemical energy which we use and need to do work.  A calorie can be defined as “the amount of energy (heat) required to raise the temperature of 1 gram (g) of water 1 degree Celsius (Cº)”.  The word calorie gets its origins from Latin as the word “calor” actually means “heat” (our umbrella topic!) in Latin.  All foods have a specific calorific value – a hamburger has many Calories, a carrot has much less. When calories are written with a capital C, as they mostly are on packaging, it means they are in fact kilocalories (there are 1000 calories in a kilocalorie).  

        A simple way to measure the energy or the calorific value found it foods is by using a calorimeter.  We used this device previously in physics to investigate latent and specific heats.  It is a device that measures the heat generated by a chemical reaction or a change in state.  What the device does is it insulates (at its best) the reaction in order to minimize heat loss.  As we ignite the apple, the calorimeter should trap the heat generated from the burning apple and the water above in the calorimeter will absorb the heat and thus raise the temperature of the water.  The heat gained by the water therefore must equal the heat lost by the apple, all things kept equal.  

                                Q lost by apple = Q gained by water

        As we have done before, we will be using a familiar formula to calculate the energy gained by the water.

Q = (m)(c)(ΔT)

        Where Q is the energy gained by the water, m is the mass of the piece that was actually burned (initial weight – final weight) and T the change in the temperature of the water.


        Since this is the first time I perform an experiment of this sort where I measure calories in a food, it would be hard to base my hypothesis on previous scientific investigations.  However using the fact that apples are mainly made out of water with some glucose, I would estimate that an apple has around 50 – 150 calories.  

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        A suggested amount for a male human daily calorie intake is around 2000 calories, and since an apple is considered “healthy” I would estimate it should be around 5% of that, so around 100 calories.  If the apple successfully combusts and not much heat energy is lost to the surrounding then I predict I will calculate that an average sized apple has roughly 100 calories and a dry apple around 20 per piece.


        The dependant variable, or what we measure in this experiment, will be amount that the temperature of the water changes.  To do this I will be ...

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