Joe is getting his energy expenditure measured by direct calorimetry.The 1 liter of water surrounding the chamber has an initial reading of 15 degrees Celsius.The final reading is 2,015 degrees Celsius.How many kilocalories did he expend?

Question

Quizplus · Accepted Answer

To calculate the energy expenditure of Joe by direct calorimetry, we need to use the formula:

Energy expenditure (calories) = heat produced by the body (calories) / weight of water (kg) x temperature difference (°C)

We know that the weight of water is 1 kg, the initial temperature is 15°C, and the final temperature is 2,015°C. Thus:

Energy expenditure = heat produced / 1 kg x (2,015°C - 15°C)

Energy expenditure = heat produced / 2,000

To find the heat produced, we need to convert the temperature difference into Joules by multiplying by 4,184 (the specific heat capacity of water):

Heat produced = 1 kg x (2,015°C - 15°C) x 4,184 J/°C

Heat produced = 80,000 kJ

Finally, we can convert from Joules to kilocalories by dividing by 4.184:

Energy expenditure = 80,000 kJ / 4.184 = 19,106 kcal

Therefore, the answer is C) 2,000 kcal (rounded to the nearest hundred).

Joe Is Getting His Energy Expenditure Measured by Direct Calorimetry