JH Academic Bowl Practice Test

Hydrogen is the flammable gas known for being far lighter than air. It’s the lightest element and forms H2 molecules, giving it a density that’s around 14 times smaller than that of air. That extreme lightness means hydrogen quickly disperses when released. These fuels—coal, oil, and natural gas—are hydrocarbons that contain hydrogen in their molecular structure, so hydrogen is the flammable element present in them. The other options don’t fit: oxygen isn’t lighter than air, nitrogen is the main nonflammable component of air, and carbon monoxide, while flammable, has a density similar to air and isn’t more than 14 times lighter.