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 region of the graph does the addition of heat cause particles to vibrate more vigorously while remaining in an otherwise locked position?

Explanation:

Step1: Understand the heating curve

In a heating curve, when a substance is in a single - phase (solid, liquid, or gas) and heat is added, the temperature rises. When there is a phase change (melting or boiling), the temperature remains constant.

Step2: Analyze each region

• Region 1: The substance is in the solid state. As heat is added, the temperature of the solid increases. In the solid state, particles are in a "locked" position (fixed lattice structure). When the temperature of the solid increases, the particles vibrate more vigorously in their fixed positions.
• Region 2: Melting (phase change from solid to liquid). Temperature is constant.
• Region 3: Liquid state. Particles are not in a "locked" position (they can move around each other).
• Region 4: Boiling (phase change from liquid to gas). Temperature is constant.
• Region 5: Gas state. Particles are free to move.

Answer:

Region 1