In the IR Imaging of IR Imaging of Heat Flow Learning Tool., you can watch both a visible light video and an IR imaging video of the hot stopper being placed in water. Watch the videos and use the following questions to test your understanding of what is happening.
In the IR imaging video, why does the area of high temperature created by the stopper eventually disappear? What has happened?
This area of high temperature 'disappears' because eventually the stopper and the water have approximately the same temperature, so the IR imaging camera cannot distinguish between them.
Based on the answer to the previous question, describe what has happened between the stopper and the water?
Since the stopper and the water have reached approximately the same temperature, heat must have flowed from the stopper to the water.
Carefully observe the color changes in the IR imaging video. How has the temperature of the stopper changed? How has the temperature of the water changed?
The temperature of the stopper has decreased, because the stopper’s color has changed from whitish to blue. The temperature of the water has increased slightly, because the water’s color has become a slightly lighter blue.
Using the temperature scale on the side of the IR imaging video, estimate the temperature change of both the stopper and the water. Has the stopper or the water experienced the larger temperature change?
At the beginning of the video, the temperature of the stopper is greater than 35 °C and the temperature of the water appears to be about 22 °C. At the end of the video, the temperature of both the stopper and the water is about 25 or 26 °C. Evidently, the temperature of the stopper has changed more dramatically than the temperature of the water has.