A 500 g block of copper is heated in an oven from 25 °C to 150 °C and then allowed to…
PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
A 500 g block of copper is heated in an oven from 25 °C to 150 °C and then allowed to cool in air until its temperature reaches 75 °C. Calorimetric measurements show that the specific heat capacity of copper is 0.385 J g⁻¹ °C⁻¹ between 0 °C and 100 °C and 0.390 J g⁻¹ °C⁻¹ between 100 °C and 200 °C. No phase changes occur at any point in the process.
(a) Describe why a chemist must divide the temperature change during the heating stage into more than one interval before calculating the total energy absorbed by the block.
(b) Without performing numerical calculations, state the algebraic sign (positive or negative) of the heat, q, for (i) the heating step and (ii) the cooling step. Justify each choice in terms of energy flow.
(c) Explain how the principle of conservation of energy applies to the complete heat–cool sequence for the copper block.