What amount of heat received water weighing 0.5 kg, if it was heated from 20 C to boiling?

To calculate the amount of heat required for heating a substance of mass m, having a specific heat capacity c, from temperature t₁ to temperature t₂, the formula is used:

Q = с ∙ m ∙ (t₂ – t₁).

It is known from the problem statement that water with a mass of m = 0.5 kg was heated from a temperature of t₁ = 20 ° C to boiling. From the reference tables, we determine the boiling point of water t₂ = 100 ° С and the specific heat of water c = 4200 J / (kg ∙ ° С). Substitute the values of the quantities into the calculation formula:

Q = 4200 J / (kg ∙ ° С) ∙ 0.5 kg ∙ (100 ° С – 20 ° С);

Q = 168000 J = 168 kJ.

Answer: the water got 168 kJ.