Question

ASSERTION-
The melting point of ice and boiling point of water are taken as the LFP and UFP of all the thermometer scales.
REASON-
Thermometer works on the principle of thermal expansion of liquids.

Answer 1

Here, we will be using the concept of working principle of the thermometer and consideration of melting point of ice and boiling point of water for the different thermometer scales. Basically thermometers are used for the purpose of temperature measurement.

Complete step by step answer:
Given, As we know that all thermometer scales have a lower fixed point (LFP) and an upper fixed point (UFP).
-We can understand the meaning of the terms LFP and UFP as lower fixed point and upper fixed point respectively. The LFP indicates the lower point which is the melting point of ice and UFP is the boiling point of water. These two points are different for the different thermometer scales but the distance between lower fixed point and upper fixed point are the same for all types of thermometer scales.
-As we know the melting point of ice and boiling point of water, we cannot be taken as the LFP and UFP for all the thermometer scales because LFP and UFP are not fixed points for all scales. For example LFP is the triple point of water in the case of the Kelvin thermometer.
-As we know, due to rise in temperature, the liquids are sensitive to expands from the original condition so the thermometer works on the principle of thermal expansion of liquids.
So we can conclude that the assertion statement is incorrect and the statement in the reason is correct.

Note: In this type of problem we should remember one thing that both the points LFP and UFP are only fixed for the ideal thermometer not for any other thermometer. For the ideal thermometer the temperature measurement is not dependent on the material properties.