How much water can be heated by 10 C, giving it 84 kJ of heat?

The amount of heat expended to heat water:
Q = C * m * ∆t, where Q is the consumed amount of heat for heating water (Q = 84 kJ = 84 * 10³ J), C is the specific heat capacity of water (C = 4.2 kJ / (kg * K) = 4 , 2 * 10³ J / (kg * K)), m is the mass of water (kg), ∆t is the change in water temperature (∆t = 10 ºС).
Let us express and calculate the mass of heated water:
m = Q / (C * ∆t) = 84 * 10³ / (4.2 * 10³ * 10) = 2 kg (2 l).
Answer: Having spent 84 kJ of heat, you can heat 2 kg (2 l) of water.