# 2 liters of water were poured into a saucepan at a temperature of 15 degrees.

**2 liters of water were poured into a saucepan at a temperature of 15 degrees. After boiling, there was 200g less water in the pan than at the beginning of heating. How much heat did the water get in the pot?**

To calculate the amount of thermal energy received by water, we use the formula: Q = Q1 (evaporation) + Q2 (heating) = L * mi + Sv * mn * (tboil – t) = L * mi + Sv * ρw * V * (tboil – t).

Data: L – beats heat of vaporization (L = 2.3 * 10 ^ 6 J / kg); mi is the mass of evaporated water (mi = 200 g = 0.2 kg); St. – beats. heat capacity of water (Sv = 4.2 * 10 ^ 3 J / (kg * ºС)); ρw is the density of the poured water (ρw = 10 ^ 3 kg / m3); V is the initial volume of water (V = 2 l = 2 * 10 ^ -3 m3); tboil – boiling point (tboil = 100 ºС); t – initial temperature (t = 15 ºС).

Calculation: Q = 2.3 * 10 ^ 6 * 0.2 + 4.2 * 10 ^ 3 * 10 ^ 3 * 2 * 10 ^ -3 * (100 – 15) = 1174000 J = 1.174 MJ.

Answer: The water in the pot should have received 1.174 MJ of thermal energy.