Energy Content in Foods

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Presentation transcript:

Energy Content in Foods Objective: To determine the energy released as various foods burn.

Premise As the food burns, it will release heat energy. We will assume that all of the heat produced will be transferred to the water in the can. We can then use the specific heat of water, the mass of water used, and the temperature change that occurs as the water heats up to calculate the amount of heat energy.

Definitions Cp = heat energy (q) mass (m) x temperature change (Δt) Specific Heat- the amount of heat energy (measured in units of Joules) it takes to raise the temperature of 1g of a substance 1 degree Celsius Cp = heat energy (q) mass (m) x temperature change (Δt) The specific heat of a substance can be used to calculate the amount of heat energy if the above equation is rearranged: q = Cp x m x Δt

Cp(water) x mass water x temp. change Calculations Mass of water heated = mass of can and water – mass of empty can Change in temperature = Final temp – initial temp. Heat absorbed by water = Cp(water) x mass water x temp. change Cp = 4.18 J/g-°C

Calculations continued… Energy content in kJ/g Convert heat absorbed by water from J to kJ by dividing by 1000 or moving the decimal three places to the left. Find mass of food burned = Initial mass of food/holder – Final mass of food/holder -Divide the kJ of heat by grams of food burned