A mercury thermometer, at an initial temperature of 20◦C, was placed in 40◦C water, and the temperature registered by the thermometer was recorded over time. This procedure was repeated using water samples at 50◦C and 60◦C (see Figure 1). Next, the same thermometer, at an initial temperature of 60◦C, was placed in an air sample at 50◦C, and the temperature registered by the thermometer was recorded over time. This procedure was repeated using air samples at 30◦C and 40◦C (see Figure 2) According to Figure 2, for an air temperature of 30°C, over which of the following time intervals was the thermometer reading changing most rapidly?

Correct answer: A. 0-100 sec.

A. 0-100 sec.
B. 100-200 sec.
C. 200-300 sec.
D. 300-400 sec.

Explanation

According to Figure 2, the dotted line represents an air temperature of 30◦. During the interval from 0-100 seconds, the dotted line moves rapidly down and to the right, showing a signiﬁcant drop in temperature. The dotted line begins to level off shortly after 100 seconds, indicating a stable temperature from about 200 seconds forward.

Last updated 3 September 2026

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