What is the normal freezing point of this unknown substance?

• A. 0 °C
• B. –200 °C
• C. 200 °C
• D. 400 °C
• E. 100 °C

Answer: (E)

Verified step by step guidance

1. Identify the graph as a phase diagram, which typically shows the relationship between temperature and a property such as pressure or volume for a substance.
2. Locate the point on the graph where the phase change occurs, which is often indicated by a change in the slope of the line. This is typically where the substance transitions from liquid to solid, known as the freezing point.
3. Observe the x-axis, which represents temperature, and find the temperature value at the point where the phase change occurs.
4. Note that the phase change point on the graph is at 100 °C, which is where the line changes slope, indicating the freezing point of the substance.
5. Conclude that the normal freezing point of the unknown substance is 100 °C, as indicated by the graph and the change in slope at this temperature.