Which type of air is denser?

Cold air is denser than warm air due to the behavior of air molecules in different temperature conditions. When air is cold, the molecules are closer together, leading to a higher density. Conversely, when air is warm, the molecules move faster and spread out, which reduces the overall density of the air.

Furthermore, while moisture content does affect air density, cold and dry air tends to be denser than warm and moist air. Moist air is less dense than dry air because water vapor is lighter than the nitrogen and oxygen molecules it displaces. Therefore, in a direct comparison, colder air is denser than warmer air, making it the correct answer in this scenario.