An aluminum engine component of mass 2.00 kg undergoes the following thermal schedule…
PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
An aluminum engine component of mass 2.00 kg undergoes the following thermal schedule during a maintenance cycle:
• Step 1: Cool from 95 °C to 20 °C as it sits on a workbench.
• Step 2: Move to a walk-in freezer where it cools further to –15 °C.
• Step 3: Reheat in an oil bath to 70 °C before reinstallation.
For aluminum, the specific heat capacity is 0.890 J g⁻¹ °C⁻¹ at temperatures above 0 °C. Below 0 °C, the specific heat capacity increases uniformly by 8 % relative to the value above 0 °C. Ignore any phase changes and assume no energy is exchanged with the surroundings except as described.
(a) Calculate the heat exchanged during Step 1.
(b) Calculate the heat exchanged during Step 2, taking into account the change in specific heat capacity.
(c) Calculate the heat exchanged during Step 3.
(d) Determine the algebraic sum of the heats for all three steps.
(e) Explain, with reference to the calculated values, whether the overall process results in a net absorption or release of energy by the aluminum component.