Question

a substance is placed in a closed vessel. the substance is continuously heated and its temperature is monitored, leading to the heating curve below. five regions of the heating curve are labeled with a number. during which numbered region of the graph is there... a mixture of solid and liquid present? tap me!... a mixture of liquid and gas present? tap me!... a mixture of solid and gas present? tap me!

Explanation:

• For a mixture of solid and liquid: During melting (phase change from solid to liquid), temperature remains constant. This is region 2.
• For a mixture of liquid and gas: During boiling (phase change from liquid to gas), temperature remains constant. This is region 4.
• For a mixture of solid and gas: There is no such region in a normal heating curve (sublimation is solid - gas without liquid, but in a typical heating curve with melting and boiling as here, there is no solid - gas co - existence region).

Answer:

• A mixture of solid and liquid: 2
• A mixture of liquid and gas: 4
• A mixture of solid and gas: None (or no region in this heating curve)