Thermal expansion of liquids
What is the thermal expansion of liquids ?
During a temperature variation, the volume of liquids changes: they contract or expand. The coefficient of thermal expansion of liquids is a parameter which makes it possible to quantify this phenomenon. For the majority of liquids, this coefficient is of the order of 10-4/K: for each degree, the volume of the fluid increases by a few ten-thousandths of times its volume.
While almost all fluids expand with a rise in temperature, there is at least one exception: between 0 and 4°C, water contracts with the rise in temperature. Over this temperature range, its coefficient of thermal expansion is then negative.
How it is measured ?
The coefficient of thermal expansion is not measured directly with a device. Its determination is carried out by calculation from precise measurements of densities carried out at several temperatures.
Coefficients of thermal expansion are determined as a function of temperature from density values using the equation opposite.
At Calnesis, the density measurements allowing the determination of the evolution of the volumetric thermal expansion coefficients of liquids are carried out with a very precise vibrating tube densimeter: the Anton Paar DMA 5000M. This device allows the measurement of density with an accuracy of 0.000001 g/cm3 over a temperature range between 0°C and 100°C.