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Method:
1. Obtain the mass of the unburnt food.
2. Place the food sample onto the combustion wire or needle (Place the food on the table and push the wire into the food. Do not use
the fi ngers to hold the food as injury may occur)
3. Start the datalogging software.
4. Ignite the food sample using the spirit burner.
5. Hold the food under the boiling tube and allow the food to fully burn and extinguish.
6. Stop the datalogging software and using the plotted graph obtain the temperature change.
7. Obtain the mass of the burnt food.
Hint: You can repeat the experiment and take an average but remember to use the same mass of food each time.
Results:
To obtain the energy released per gram of food burnt, substitute your values into the following:
Energy transferred (J) = mass of water (kg) x specifi c heat capacity of water (J/kg
O
C) x rise in temperature (
O
C)
So Energy transferred (J) = 0.025 x 4200 x rise in temperature (
O
C) (Note: 25 ml of water has a mass of 25 g (0.025kg))
Therefore the energy transferred by each gram of food burnt is given by:
Energy transferred by each gram (J/g) = [0.025 x 4200 x rise in temperature (
O
C)]
mass of food burnt (g)
How accurate do you think the results are?
Has all of the heat energy released by the food been used to heat the water?
What effect does heat loss have on the results?
Going further:
What factor could you vary in this investigation in order for it to be a fair test?
How important is the amount of energy in food to different people such as athletes?
What about the food industry. How is this process useful in food production?
Where might this information be found for different foods?
Biology