When a mercury-in-glass thermometer is placed in boiling water, the initial drop in the mercury column can be attributed to the thermal expansion of the glass, which momentarily contracts the mercury before it begins to expand. Heat transfer occurs primarily through conduction from the glass to the mercury, causing the mercury to eventually rise as it absorbs heat. The phenomenon illustrates the principles of thermal conductivity and the response of materials to temperature changes. Concerns about similar conceptual questions appearing on the AP exam are noted, with past experiences indicating such questions are rare. Understanding these concepts is crucial for grasping the behavior of thermometers in varying temperatures.
