Final answer:
Cold air contains more molecules per unit volume and therefore is denser than warm air. This is due to the lower kinetic energy of the particles at lower temperatures, explained by the Ideal Gas Law, which results in a higher density.
Step-by-step explanation:
The student's question relates to the density of air at different temperatures. Cold air has more molecules per unit volume compared to warm air because the particles are moving slower, allowing them to be closer together. This results in cold air having higher density. On the contrary, hot air is less dense due to the increased speed and energy of its particles causing them to occupy a larger volume.
The phenomenon where hot air is less dense than cold air is because the molecules in the hot air are moving more rapidly, which is explained by the Ideal Gas Law. The energy which the molecules possess causes them to spread out more, occupying a greater volume and thus having a lower density. This explains why hot air rises over cooler air.
In contrast, when air is cooled, its molecules slow down and are able to occupy less volume, resulting in a more tightly packed arrangement of molecules. This increase in molecules per cubic centimeter contributes to the higher density of cold air. This concept is commonly applied in various scientific disciplines, including meteorology, thermodynamics, and environmental sciences.