Which gas has the highest specific gravity?

Butane has the highest specific gravity among the options provided. Specific gravity refers to the ratio of the density of a substance to the density of a reference substance, usually water for liquids or air for gases. In the case of gases, substances with higher specific gravities are heavier than air, causing them to settle or accumulate at lower levels in an environment.

Butane, typically used in heating and cooking applications, has a specific gravity of approximately 2.00 when compared to air. This means butane is significantly denser than the other gases listed. In contrast, natural gas, primarily composed of methane, has a specific gravity of about 0.60, and propane has a specific gravity of around 1.50, both of which are lighter compared to butane. Therefore, when considering applications involving gas storage and safety, understanding the specific gravity of these gases is crucial for proper handling and ventilation practices.