Answer to Question #94081 in Molecular Physics | Thermodynamics for Amaechi Onuh

Question

Mention two factors that can change the fixed points of a temperature scale

Answer 1

All temperature scales are calibrated according to the thermal properties of a particular substance or device. Typically, this is established by fixing two well-defined temperature points and defining temperature increments via a linear function of the response of the thermometric device. For example, both the old Celsius scale and the Fahrenheit scale were originally based on the linear expansion of a narrow mercury column within a limited temperature range, each using different reference points and scale increments.

Different empirical scales may not be compatible with each other, except for small regions of temperature overlap. If an alcohol thermometer and a mercury thermometer have the same two fixed points, namely the freezing and boiling point of water, their reading will not agree with each other except at the fixed points, as the linear 1:1 relationship of expansion between any two thermometric substances may not be guaranteed.