When bubbles form in a liquid that is being heated, what process has occurred?

• A. The liquid is dissolving a gas from the atmosphere.
• B. The liquid is cooling and forming solid particles.
• C. The liquid is undergoing sublimation.
• D. The liquid is undergoing a phase change from liquid to gas (boiling).

Answer: (D)

Verified step by step guidance

1. Understand that when bubbles form in a liquid being heated, it indicates a change in the state of the substance within the liquid.
2. Recall that bubbles in a heated liquid are typically pockets of vapor forming inside the liquid, which is a sign of boiling.
3. Recognize that boiling is a phase change where the liquid turns into gas throughout the bulk of the liquid, not just at the surface.
4. Eliminate other options: dissolving gas from the atmosphere involves gas entering the liquid, cooling and forming solids refers to freezing or crystallization, and sublimation is a direct solid-to-gas transition without passing through liquid.
5. Conclude that the formation of bubbles during heating corresponds to the liquid undergoing a phase change from liquid to gas, known as boiling.