PHYSICS · Multi-part · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter
Problem
Two transparent, sealed containers are placed side-by-side on a laboratory bench at 1 atm pressure.
• Container I holds a thin slab of ice that is exactly at its melting point (0 °C). The bench lamp warms the container until all of the ice has just melted, after which the liquid water remains at 0 °C.
• Container II holds water vapor that is exactly at its condensation point (100 °C). The vapor is slowly cooled until it has completely condensed to liquid water at 100 °C.
Assume that heat exchange occurs only between each container and the surrounding room air; no work is done by either system.
For each container, answer the following questions.
(a) Describe the direction of energy transfer between the system in Container I and its surroundings while the phase change occurs.
(b) Classify the phase change in Container I as endothermic or exothermic, and explain your reasoning in terms of energy changes at the particulate level.
(c) For Container II, identify the direction of energy transfer and classify the phase change as endothermic or exothermic.
(d) Compare the particulate-level descriptions of the two phase changes, focusing on the changes in intermolecular forces and the corresponding energy flow.