WAEC - Physics (2015 - No. 16)
Water is unsuitable for use as a thermometric liquid because it
expands unevenly between 0oC and 40oC
has narrow temperature range
has a concave meniscus
maintains a fixed density
Paliwanag
Water's freezing point is 0°C and its boiling point is 100°C at standard atmospheric pressure, which provides a limited temperature range for measurement compared to other liquids used in thermometers. Other liquids like mercury can measure a wider range of temperatures.