Which statement correctly describes glycerol's effect on soap bubble longevity?

• A. It reduces the color variety of bubbles.
• B. It accelerates bubble evaporation.
• C. It adheres to water molecules, helping to mitigate evaporation.
• D. It causes the bubble film to crack more easily.

Answer: (C)

Glycerol helps soap bubbles last longer by slowing water loss from the film. It’s hygroscopic, so it attracts and holds water in the bubble film. By binding water, glycerol reduces evaporation, keeping the film thicker and more flexible for a longer time. This combination extends bubble longevity, which is why describing glycerol as sticking to water molecules and helping mitigate evaporation fits best. The other ideas—that glycerol changes color variety, speeds up evaporation, or makes the film crack more easily—don’t align with how glycerol actually stabilizes the film; in fact, it tends to make the film more viscous and elastic and less prone to cracking.