Calculate the amount of heat required to melt 7 kg of copper having an initial temperature of 585 ° C.

m = 7 kg.

t = 585 ° C.

tc = 1085 ° C.

λ = 2.1 * 10 ^ 5 J / kg.

С = 381 J / kg * ° С.

Q -?

To melt copper, it must first be heated from temperature t to boiling point tc, and then transferred from solid to liquid.

The amount of heat Q will be the sum of the amount of heat Q1 for heating and the amount of heat for melting Q2.

Q = Q1 + Q2.

The amount of heat Q1 required for heating copper is determined by the formula: Q1 = C * m * (tc – t), where C is the specific heat capacity of copper, m is the mass of copper, tc, t is the final and initial temperature of copper.

The amount of heat Q2 required to melt copper at the melting temperature is determined by the formula: Q2 = λ * m, where λ is the specific heat of melting of copper.

Q = С * m * (tк – t) + λ * m = m * (С * (tк – t) + λ).

Q = 7 kg * (381 J / kg * ° C * (1085 ° C – 585 ° C) + 2.1 * 10 ^ 5 J / kg) = 2803500 J.

Answer: to melt copper, you need Q = 2803500 J of thermal energy.