Question

Fat has energy content of 9.2 kcal/gram. If a person ate 1oz of fat that was completely converted to heat. How much water could be raised from room temperature to the boiling point?

1oz = 28.35g Room temp = 70 degrees F Boiling point 212 degrees F 1kcal = 1,000cal 1cal = 1g water up 1 degree F

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Answer 1

1 oz = 28.35 g

1 g fat will give an energy of 9.2 kCal

total energy released = 9.2 x 28.35 = 260.82 kCal

on converting to J = 260.82 x 4.184 = 1091.27 x 10³ J

Heat energy relased = specific capacity of water x mass of water x change in temperature

70 degrees F = 21.1 degree celsius

Boiling point of water = 100 degree celsius

Change in temperature = 78.9 degree celsius.

1091.27 x 10³ = 4.184 x 78.9 x mass of water

mass of water = 3.3 x 10³ g = 3.3 kg = 3.3 L