Three independent processes are described below. For each process, consider the system identified in parentheses.
• Process I – A student holds an ice cube (system: the ice).
• Process II – A piece of iron at 150 °C is dropped into a beaker of water at 25 °C (system: the iron).
• Process III – Solid ammonium nitrate is dissolved in water; the solution temperature falls from 22 °C to 17 °C (system: the dissolving salt and resulting solution).
Assume that pressure is constant and that no work other than pressure–volume work occurs.
(a) For each process, indicate the direction of heat flow (into the system or out of the system) and state whether the process for the system is endothermic or exothermic.
(b) For each process, assign the appropriate algebraic sign (positive, negative, or zero) to qsystem. Justify each sign in terms of the temperature change of the surroundings.
(c) Compare the magnitudes of ∣qsystem∣ for Process I and Process III, given that the mass of ice held is 5 g and the mass of ammonium nitrate used is 1 g. Provide a qualitative explanation without performing numerical calculations.