Which gas is flammable and gives a squeaky pop when lit?

• A. Ammonia
• B. Carbon Dioxide
• C. Oxygen
• D. Hydrogen

Answer: (D)

Flammable gases that burn with a distinctive sound when lit show a quick, energetic reaction. Hydrogen is highly flammable and, when ignited with a splint, it burns with a characteristic squeaky pop. The rapid combustion of hydrogen with oxygen forms water, releasing energy in a very short burst. That sudden release creates a small pressure wave in the confined space, producing the sharp popping noise you hear. The other gases don’t fit this cue: carbon dioxide doesn’t burn and tends to extinguish flames, oxygen itself doesn’t burn, and ammonia isn’t known for producing that pops in a simple test. So hydrogen best matches both the flammability and the squeaky pop.