How much heat is required to heat 2 kg of water from 20 to 70 C?

The required amount of heat is calculated using the following formula:
Q = C * m * Δt, where C is the specific heat capacity of water (we take C = 4200 J / (K * kg)), m is the mass of heated water (m = 2 kg), Δt is the change in water temperature (the difference between the final and initial temperatures Δt = 70 ° С – 20 ºС = 50 ºС).
Let’s do the calculation:
Q = 4200 * 2 * 50 = 420,000 J or 420 kJ.
Answer: To heat 2 kg of water, 420 kJ of heat is required.