A thermometric property is a physical property that varies continuously with temperature.
Thermometric properties can be used to measure the temperature. Thermometric properties commonly used for thermometers include:
Volume: Most objects expand when they are heated.
The volume of mercury or alcohol expands when the temperature increases. Both are often used in thermometers.
The resistance of a copper wire increases with temperature. Resistance thermometers use the resistance of copper or other metals to measure temperature.
The mass of an object does not change when an object is heated. Mass is not a thermometric property.
A thermometric property should be easily measurable.
People shiver when they get cold but this is not a good thermometric property. Shivering does not change continuously above a certain temperature (when it is warm) and shivering is difficult to measure.