Increasing order of surface tension water methyl cyanide or methyl alcohol
Answers
In Unit 2, we discussed the characteristics of ideal gases. We assumed that there is no
attractive or repulsive interaction between the individual molecules. In Unit 3, this
treatment was modified to account for the behaviour of real gases'at low-temperatures and
high pressures and to explain the liquefaction of gases. Finite size of the gaseous molecules
and their weak interaction were recognised. In Unit 5, we are going to study the strong
interactions in a solid crystal and the orderly arrangement of particles in it. In this unit, we
will discuss the characteristics of liquids in contrast to those of gases and solids. Our aim is
not to list the properties of liquids but to correlate these to the intermolecular interactions.
We will describe the features of a model proposed for the structure of liquids. We shall
explain the correlation between the intermolecular forces and the properties of liquids such
as surface tension, viscosity, vapour pressure, boiling point and molar enthalpy of
vaporization. Finally we will briefly study liquid crystals, their types and their applications.
Objectives
After studying this unit, you should be able to :
explain the structure of liquids,
state the significance of surface tension and viscosity of liquids,
discuss the qualitative dependence of vapour pressure, boiling point and molar enthalpy
: of vaporization of liquids on the molecular interactions,
state and explain Trouton's rule, and
discuss the types of liquid crystals and their applications.