# How much heat is needed to heat 5kg of water from 20 degrees to boiling and evaporate all the water?

**How much heat is needed to heat 5kg of water from 20 degrees to boiling and evaporate all the water? Specific heat capacity of water С = 4200J / kg degrees. Specific heat of vaporization of water r = 2.3 * 10 in the sixth power J / kg**

Given:

m = 5 kilograms is the mass of water;

T1 = 20 degrees Celsius – initial water temperature;

T2 = 100 degrees Celsius – boiling point of water;

c = 4200 J / (kg * C) – specific heat of water;

q = 2.3 * 10 ^ 6 J / kg is the specific heat of vaporization of water.

It is required to determine the amount of heat Q (Joule) required to heat to a boil and evaporate water.

Let’s find the heat that needs to be spent to heat the water to the boiling point:

Q1 = c * m * (T2 – T1) = 4200 * 5 * (100 – 20) = 21000 * 80 = 1680000 Joules.

Let’s find heat to evaporate water:

Q2 = q * m = 2.3 * 10 ^ 6 * 5 = 11,500,000 Joules.

Then the total amount of heat will be equal to:

Q = Q1 + Q2 = 1680000 + 11500000 = 13180000 Joules = 13.2 MJ.

Answer: it is necessary to expend heat equal to 13.2 MJ.