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A student eats 2000 kcal per day. (a) Assuming that all of the food energy is released as heat, what is the rate of heat released (in watts)? (b) What is the rate of change of entropy of the surroundings if all of the heat is released into air at room temperature \(\left(20^{\circ} \mathrm{C}\right) ?\)

Short Answer

Expert verified
Question: Calculate (a) the rate of heat released in watts and (b) the rate of change of entropy of the surroundings when a student consumes 2000 kcal per day and the heat is released into the air at room temperature (20°C). Answer: (a) The rate of heat released is approximately 96.85 W. (b) The rate of change of entropy of the surroundings is approximately 0.3306 W/K.

Step by step solution

01

Convert Calories to Joules

First, we need to convert the 2000 kcal into joules. Recall that 1 kcal = 4184 J. So we have: 2000 kcal/day × (4184 J/kcal) = 8,368,000 J/day
02

Convert the Energy to Power

To find the rate of heat released in watts, we need to convert joules to watts. Recall that power (W) is energy per unit time (J/s), and we are given energy per day. Since 1 day = 86400 seconds, we can use the following conversion: 8,368,000 J/day × (1 day/86400 s) = 96.85185 W
03

Calculate the Rate of Change of Entropy

We are given the room temperature as 20°C, which we need to convert to Kelvin. The Kelvin temperature can be found by adding 273.15 to the Celsius temperature: \(T = 20 + 273.15 = 293.15 K\) Now, we can use the following formula to find the rate of change of entropy: \(\frac{dS}{dt} = \frac{P}{T}\) where \(\frac{dS}{dt}\) is the rate of change of entropy, \(P\) is the power in watts, and \(T\) is the temperature in Kelvin. Substitute our calculated values into the formula: \(\frac{dS}{dt} = \frac{96.85185 W}{293.15 K} = 0.3306 \frac{W}{K}\) #Conclusion# The rate of heat released as the student consumes 2000 kcal per day is approximately 96.85 W, and the rate of change of entropy of the surroundings is approximately 0.3306 W/K.

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