Which type of air is lighter?

Warm air is lighter than cold air because of the way temperature affects air density. As air is heated, the molecules within it gain energy and move more rapidly, which causes them to spread apart. This increase in molecular activity results in a decrease in density, allowing warm air to rise.

In contrast, cold air is denser because its molecules are more closely packed together, causing it to sink. This principle is fundamental in meteorology and contributes to various weather patterns and phenomena.

Stable air refers to a condition where the atmosphere resists vertical motion, not specifically tied to its weight or density compared to warmer or colder air. Dry air, while potentially lighter than moist air due to less water vapor, does not inherently compare to warm versus cold air in weight. Thus, the relationship between temperature and air density directly supports the understanding that warm air is lighter.