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 move about the entire container at even higher speeds?

Explanation:

Step1: Analyze the heating curve regions

• Region 1: Solid state, particles vibrate in fixed positions.
• Region 2: Melting (solid - liquid phase change), temperature constant.
• Region 3: Liquid state, particles move more freely than in solid.
• Region 4: Boiling (liquid - gas phase change), temperature constant.
• Region 5: Gas state. In a gas, particles move freely throughout the container. As heat is added in region 5 (since it is a single - phase region for gas), the temperature of the gas increases. According to the kinetic - molecular theory, as the temperature of a gas increases, the average kinetic energy of its particles increases. Kinetic energy \(K = \frac{1}{2}mv^{2}\), so an increase in kinetic energy (with mass \(m\) of particles constant) means an increase in the speed \(v\) of the particles.

Answer:

Region 5