The fuel value of hamburger is approx. 3.7 kcal/g. If a man eats 0.45 lbs of hamburger for lunch and none of the energy is stored in his body, estimate the amount of water that would have to be lost in perspiration to keep his body temperature constant. The heat of vaporization of water may be taken as 2.41 kJ/g. (1 lb = 453.6g)

Answer: ______ kg

Convert 0.45 # hamburger to grams

0.45 lb x (453.6 g/lb)= ?? grams hamburger.
?? g hamburger x 3.71 kcal/g = xx kcal.
I would convert that to kJoules.
xx kcal x (4.184 kJ/kcal) = yy kJ.
Then mass water x delta Hvap = yy kJ
Solve for mass water. I get something a little over 1 kg.

To calculate the amount of water that needs to be lost in perspiration, we need to determine the energy content of the hamburger consumed by the man and then find the amount of water required to dissipate that energy through the process of perspiration.

Step 1: Convert the weight of the hamburger from pounds to grams:
0.45 lbs = 0.45 * 453.6 g = 204.12 g

Step 2: Calculate the energy content of the hamburger consumed:
Energy content = weight of hamburger * fuel value
Energy content = 204.12 g * 3.7 kcal/g = 755.844 kcal
(Note: 1 kcal = 4.184 kJ)

Step 3: Convert the energy content to kilojoules:
Energy content = 755.844 kcal * 4.184 kJ/kcal = 3161.91 kJ

Step 4: Determine the amount of water required to dissipate this energy:
Amount of water = Energy content / heat of vaporization of water
Amount of water = 3161.91 kJ / 2.41 kJ/g = 1312.14 g

Step 5: Convert the amount of water from grams to kilograms:
Amount of water = 1312.14 g * (1 kg / 1000 g) = 1.31214 kg

Therefore, the approximate amount of water that would have to be lost in perspiration to keep the man's body temperature constant after consuming 0.45 lbs of hamburger is approximately 1.31214 kg.

To calculate the amount of water that would need to be lost in perspiration to keep the body temperature constant, we need to determine the energy that needs to be dissipated.

First, we need to convert the weight of hamburger from pounds to grams. Given that 1 lb is equal to 453.6g, we can calculate as follows:

0.45 lbs * 453.6 g/lb = 204.12 g

Next, we need to calculate the energy obtained from eating the hamburger. The fuel value is given as 3.7 kcal/g.

Energy from hamburger = 3.7 kcal/g * 204.12 g = 754.244 kcal

Since 1 kcal is equal to 4.184 kJ, we can convert the energy obtained from eating the hamburger to kilojoules:

Energy from hamburger = 754.244 kcal * 4.184 kJ/kcal = 3153.104 kJ

Now, we can calculate the amount of water that would need to be lost to dissipate this energy. The heat of vaporization of water is given as 2.41 kJ/g.

Amount of water lost = Energy from hamburger / Heat of vaporization of water

Amount of water lost = 3153.104 kJ / 2.41 kJ/g

Amount of water lost = 1308.857 g

Finally, to convert this amount to kilograms, we divide by 1000:

Amount of water lost = 1308.857 g / 1000 = 1.309 kg

Therefore, the estimated amount of water that would need to be lost in perspiration to keep the body temperature constant is approximately 1.309 kg.