A thermos with a capacity of 3 liters was filled with boiling water.

A thermos with a capacity of 3 liters was filled with boiling water. After a while the temperature dropped to 70 ° C. How much heat came out of the thermos?

The amount of heat that came out of the thermos can be calculated using the formula:
Q = C * m * (tc – tn), where Q is heat loss (J), C is the specific heat capacity of water (C = 4200 J / (kg * K)), m is the mass of water (3 l = 3 kg) , tк – final water temperature (tк = 70 ºС), tн – initial water temperature (tн = 100 ºС).
Let us express and calculate the heat loss in a thermos:
Q = С * m * (tк – tн) = 4200 * 3 * (70 – 100) = -378000 J = – 378 kJ.
Answer: Heat loss in the thermos was 378 kJ.