A 10 g sample of an unknown substance is cooled from 150 °C (vapor) to −25 °C (solid)
PHYSICS · Subjective · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter
Problem
A 10 g sample of an unknown substance is cooled from 150 °C (vapor) to −25 °C (solid). During cooling, the vapor condenses at 110 °C and the resulting liquid freezes at 30 °C. List the phase changes that occur in order and, for each one, state whether the process is endothermic or exothermic for the substance, justifying your answer in terms of heat flow between the substance and its surroundings.