Initial data: m (mass of water) = 4 kg; tн (water temperature before cooling) = 20 ºС.
Constants: t (thermal transition temperature) = 0 ºС; C (specific heat) = 4200 J / (kg * K); λ (specific heat of crystallization of water) = 340 * 10 ^ 3 J / kg.
The released amount of heat is calculated by the formula: Q = Q1 + Q2 = C * m * (tн – t) + λ * m.
Let’s calculate: Q = (4200 * 4 * (20 – 0) + 340 * 10 ^ 3 * 4 = 1696000 J ≈ 1.7 MJ.
Answer: When 4 kg of water turns into ice, 1.7 MJ will be released.
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