🔍 Key Concepts

• Phase-change diagram for water: ice → water → steam • Difference between latent heat (flat temperature line during phase change) and sensible/superheat (sloping line where temperature rises) • Meaning of latent heat of fusion vs latent heat of vaporization and where these occur on the graph

💭 Think About

• Look at line #5: is the temperature staying constant or increasing as more BTU per pound is added? What does that tell you about the type of heat involved? • Compare line #5 with the horizontal section at 212°F. Which section represents the actual liquid-to-steam phase change, and which represents heating after the change is complete? • Where on the diagram does ice change to water, and water change to steam? Based on that, what physical process is taking place during line #5?

✅ Before You Answer

• Verify whether line #5 is above or below the 212°F boiling point line on this diagram. • Confirm if phase is changing (liquid to vapor or solid to liquid) or if the phase is already steam during line #5. • Match each choice with the correct region of a standard water heating curve: fusion near 32°F, vaporization at 212°F, superheat above saturation, sublimation direct solid-to-vapor.