In a typical phase diagram of water, which numbered point on the graph represents the phase change known as melting?

• A. 4: The triple point where all three phases coexist
• B. 2: The point where liquid transitions to gas
• C. 3: The point where gas transitions to solid
• D. 1: The point where solid transitions to liquid

Answer: (D)

Verified step by step guidance

1. Understand that melting is the phase change from solid to liquid.
2. Identify the point on the phase diagram where the solid phase region meets the liquid phase region.
3. Recognize that this boundary line represents the melting (or freezing) curve.
4. Locate the numbered point on the diagram that lies on this solid-liquid boundary line.
5. Confirm that this point corresponds to the transition from solid to liquid, which is the melting point.