Exam-style question
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When interpreting heating data, what does a plateau in the temperature graph indicate?.
- A.The substance is cooling down.
- B.The substance is undergoing a phase change.
- C.The substance is heating up rapidly.
- D.The substance has reached thermal equilibrium.
Model answer
What a good answer should say
- The substance is undergoing a phase change.
Explanation
Why this works
The evidence of a plateau in the temperature graph indicates that the temperature remains constant despite the input of heat. This shows that the substance is undergoing a phase change, such as melting or boiling.
The implication is that energy is being used to change the state rather than increase the temperature. Thus, we conclude that the plateau represents a phase change.
Common mistake
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