Procedure – Energy Content of Food Samples

Complete the table below using your results from each data run, the mass of water found under the Activity Form tab, and the information found under the Background tab.

Tip: See “Calculating Energy Content of Food Samples” under the Background tab.

Note that change in temperature = final temperature – initial temperature.

SampleFinal Temperature C)Initial Temperature C)Change in Temperature C)Mass of Water (g)Energy Transferred to Water (cal)
Blue Potato56.820.036.8  
Fatty Nut92.020.072.0  
Lean Meat63.220.043.2  

Observations and Questions

[1] What is the “Change in Temperature” for the Blue Potato sample? Show your calculation. (The temperature change is an absolute number; that is, it is a positive value.) Enter your answer in the Table above.

56.8-20= 36.8

[2] What is the “Change in Temperature” for the Fatty Nut sample? Show your calculation. (The temperature change is an absolute number; that is, it is a positive value.) Enter your answer in the Table above.

92-20=72

[3] What is the “Change in Temperature” for the Lean Meat sample? Show your calculation. (The temperature change is an absolute number; that is, it is a positive value.) Enter your answer in the Table above.

63.2-20=43.2

[4] Discuss (compare and contrast) the temperature differences that you recorded for the three samples.

[5] Re-visit the Calculating Energy Content of Food Samples section in the Background reading. In your own words, discuss the meaning of the specific heat of water which is represented by the formula: specific heat of water = 1.00 cal/(g °C).

[6] Given that 1.00 calorie is needed to increase the temperature of 1.00 gram of water by 1.00 degree Celsius, what information or data results can you use to determine how the temperature change relates to the ‘Energy transferred’ to the water by the burning food sample? Explain your answer.

[7] In your own words, discuss how the word equation below provides a hint about how to calculate the ‘Energy transferred’ to the water by each burning food sample.

Energy transferred to water = change in temperature × mass of water × specific heat of water

[8] Use the equation below to calculate the ‘Energy transferred to water’ for each sample. Enter your answers in the Table above. Show your calculation for each sample.

Blue Potato

Energy transferred to water = change in temperature × mass of water × 1.00 cal/(g °C).

Fatty Nut

Energy transferred to water = change in temperature × mass of water × 1.00 cal/(g °C).

Lean Meat

Energy transferred to water = change in temperature × mass of water × 1.00 cal/(g °C).

[9] Refer to the word equation below and, in your own words, explain why it is useful to know the energy content per gram of a food sample.

Energy content per gram = Energy transferred to water  ¸ mass of food sample

[10] Use the equation below to calculate the ‘Energy content per gram’ for each sample. Show your calculation for each sample. (See the Activity Form tab for food sample masses.)

Tip: See “Calculating Energy Content of Food Samples” under the Background tab.

Blue Potato

Energy content per gram = Energy transferred to water  ¸ mass of food sample

Fatty Nut

Energy content per gram = Energy transferred to water  ¸ mass of food sample

Lean Meat

Energy content per gram = Energy transferred to water  ¸ mass of food sample

[11] For each sample, discuss your expectation about its macronutrient composition based on the name of the sample as well as on the result obtained in question [10]. Be sure to explain whether your calculated ‘energy content per gram’ corroborates what you would expect based on the name of the sample.

[12] The food samples used in this experiment were dried, dehydrated samples. How might your data for temperature change and energy transfer differ if hydrated samples had been used?

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