CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A student claims, "When you open the freezer door, a wave of ‘coldness’ flows out because cold air is heavier than warm air." Evaluate this statement using kinetic molecular theory (KMT).
(a) Identify two specific misconceptions in the student’s statement.
(b) Using particle-level reasoning, describe what actually happens to the speed and average kinetic energy of air molecules when the temperature decreases.
(c) Explain why cooler air tends to sink relative to warmer air without invoking a substance called "cold." In your answer, explicitly connect particle motion to macroscopic density.
(d) Rewrite the student’s original sentence so that it is scientifically accurate and consistent with KMT terminology.