The Chemistry of Liquids, Part 1 - Introduction

Greetings,

Liquids are an intermediate state of matter between solids and gases.  The liquid state does not have a definite order but does consist of some intermolecular attractions which also exist in the solid state.  On the other hand, the liquid state resembles the gas state in that there is a relatively high level of disorder and kinetic energy.

Pure liquids at ambient conditions are almost always molecular compounds.  The properties of ionic compounds keep them as solids at ambient conditions.  A pure liquid has properties resulting from the 1) size, 2) elements, and 3) structure of its molecules.

Liquids consist of particles with relatively low kinetic energies (of motion).  Intermolecular forces become stronger as the speed (and kinetic energy) of molecules decrease.  All molecular liquids have van der waal's forces holding molecules together.  The van der waal's forces (also called London dispersion forces) are relatively weak and are set up by very short-lived dipole moments across individual atoms.  Van der waal's forces dominate in less polar liquids and become stronger for heavier (larger) atoms.  An example of a lower polarity liquid is carbon tetrachloride, which consists of perfectly symmetrical molecules.  Liquids consisting of assymetrical molecules, such as water, tend to have polar bonding (H-bonding for water) as the dominate intermolecular force.  Polar bonds result from electrostatic attractions between molecules with permanent dipole moments (i.e. across the entire molecule).

My next post will explain properties of liquids as they relate to intermolecular attractions.

Thank you for reading!

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