# When melting a bar of copper weighing 150 grams, 600 kJ of energy was expended.

When melting a bar of copper weighing 150 grams, 600 kJ of energy was expended. what is the mass of the bar if the initial temperature is 22 degrees Celsius.

Data: Q (energy expended when melting a copper bar) = 600 kJ = 600 * 10 ^ 3 J; t0 (initial temperature of the bar) = 22 ºС.
Reference values: tmelt (melting point of copper) = 1084.5 ºС; C (specific heat of copper) = 400 J / (kg * K); λ (specific heat of fusion of copper) = 2.1 * 10 ^ 5 J / kg.
Formula: Q = C * m * (t – t0) + λ * m = m * (C * (t – t0) + λ), whence m = Q / (C * (t – t0) + λ) = 600 * 10 ^ 3 / (400 * (1084.5 – 22) + 2.1 * 10 ^ 5) = 0.945 kg or 945 g.
Answer: The mass of the bar is 945 g.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.