Matching Phase Transition Labels to Arrow Directions

Steps:

• Recall definitions: freezing changes liquid to solid; condensing changes gas to liquid; melting changes solid to liquid; evaporating changes liquid to gas.
• Examine arrow directions in the diagram: one points from liquid to solid, another from gas to liquid.
• Match labels to directions: arrow liquid → solid requires "freezing"; gas → liquid requires "condensing".
• Compare choices: select sequence where labels align with these directed changes between solid, liquid, and gas.

Why D is correct:

• D labels the liquid-to-solid arrow as freezing and gas-to-liquid arrow as condensing, matching standard thermodynamic definitions of exothermic phase transitions.

Why the others are wrong:

• A mislabels solid-to-liquid as freezing (should be melting) and liquid-to-gas as evaporating (direction mismatch).
• B mislabels solid-to-liquid as melting (correct) but liquid-to-gas as condensing (should be evaporating).
• C correctly labels solid-to-liquid as melting and liquid-to-gas as evaporating but ignores reverse directions.

Final answer: D