When water is heated from 15 to 100 C, its internal energy will increase by 178.8 kJ. Find the mass of water to be heated.

The amount of heat required to heat water:
Q = C * m * (tк – tн), where Q is the consumed amount of heat (Q = 178.8 kJ = 178.8 * 10³ J), C is the specific heat capacity of the metal (C = 4200 J / (kg * K) ), m – mass of water (kg), tк – final water temperature (tк = 100 ºС), tн – initial water temperature (tн = 15 ºС).
Let us express and calculate the mass of heated water:
m = Q / (С * (tк – tн)) = 178.8 * 10³ / (4200 * (100 – 15)) = 0.5 kg.
Answer: The mass of heated water is 0.5 kg.