How much heat should be transferred to 2 liters of water, at a temperature of 15 ° C, until it boils?

To bring water from a certain initial temperature t₁ to the boiling point t₂, it will be necessary to transfer the amount of heat to it: Q = s ∙ m ∙ (t₂ – t₁), where m is the mass of water, s is the specific heat capacity of water. From the reference tables we find c = 4200 J / (kg ∙ ° C). The mass of water is determined by the formula: m = ρ ∙ V. We get:

Q = с ∙ ρ ∙ V ∙ (t₂ – t₁), where ρ is the density of water.

From the reference tables we find ρ = 1000 kg / m ^ 3. From the condition of the problem it is known that V = 2 L = 0.002 m ^ 3 of water was heated at a temperature of t₁ = 15 ° C until its boiling t = 100 ° C. Substitute the values ​​of the quantities into the calculation formula:

Q = 4200 J / (kg ∙ ° С) ∙ 1000 kg / m ^ 3 ∙ 0.002 m ^ 3 ∙ (100 ° С – 15 ° С);

Q = 714000 J = 714 kJ.

Answer: water needs to transfer 714 kJ.