Converting between Celsius and kelvin scales To convert between Celsius and kelvin, we use the following formula:
Converting between Celsius and kelvin t (°C) = T (K) – 273.15
For example: 0 °C = 273.15 K 100 °C = 373.15 K
Thermometric properties
To measure temperature using these temperature scales, we need to find measurable physical properties related to temperature change. These are known as thermometric properties.
Examples of thermometric properties
Length of liquid column Length of the liquid column is probably the most commonly used thermometric property. It is the one involved in many thermometers (alcohol or mercury).
As liquids rise in temperature, they expand. The temperature reading you take is from a scale that measures the length of the column of liquid in the glass tube (Fig. 10.3).
A thermometric property is a physical property that changes measurably and repeatedly with temperature change.
NOTE
Think carefully about this definition. It means you have to use only those physical changes that you can actually measure.
FIG. 10.3 The column of liquid in a thermometer expands and rises to give a temperature reading
Gas pressure or volume
The two thermometric properties of (a) the pressure of a gas at constant volume and (b) the volume of a gas at constant pressure can be studied using similar equipment, for example a syringe that has been sealed at one end but has a fixed mass of gas contained in it by the plunger (Fig. 10.4).
