7 - The liquid state
Published online by Cambridge University Press: 05 June 2012
Summary
Structure of liquids
In one of the twentieth century's greatest didactic works on science, the encyclopedic Course of Theoretical Physics of Landau and Lifshitz, there appears the following statement:
Unlike solids and gases, liquids do not allow a general calculation of their thermodynamic quantities or even their temperature dependence. The reason for this is the presence of strong interactions between the molecules of the liquid without having at the same time the smallness of the vibrations which makes the thermal motion of solids so simple. The high intensity of the molecular interaction makes it important to know, when calculating thermodynamic quantities, the actual law of interaction, which varies for different liquids. The only thing which can be done in general form is the study of the properties of liquids near absolute zero. The principles involved in this question are of considerable interest although in practice there exists only one substance (helium) which can remain liquid down to absolute zero.
At the time that was written it was indeed true that there was no general theory of liquids – that the only liquid whose properties could be derived from statistical mechanics was liquid helium, and then only in the neighborhood of the absolute zero of temperature. Now, a generation later, the situation has been wholly transformed, and we are able to calculate the properties of ordinary liquids with nearly as much assurance as we do those of dilute gases and harmonic solids.
- Type
- Chapter
- Information
- Statistical MechanicsA Concise Introduction for Chemists, pp. 101 - 132Publisher: Cambridge University PressPrint publication year: 2002