Question

Why did you work with temperatures that were about 15 ̊C above or below room temperature? Heat of Fusion and Vaporization – Calibration of a Thermometer

Answer 1

In the process of calibration, the transfer of heat between source and system is requird to be observed. Incase the temperature is very near to the temperature of surroundings, i.e. the room temperature, the change in the source temperature will take a long duration and it is hardly observable.

BUt when we take 15^o higher or lower, then the change can be observed and we can take many points on scale and thats how we can calibrate the thermometer by experimently measuring the heat transfer at a temperature difference of 15^o or more.