The Three States Of Matter
The motions of molecules in the three states of matter are shown in this animation. In the solid state the molecules remain in their lattice positions but oscillate in those positions. In the liquid state the molecules are free to translate through the entire container. Of course they also rotate or tumble during their travels. In the gaseous state, the molecules also translate and rotate but they are separated from each other by much larger distances than they are in the solid and liquid states.
A Pictorial Representation Of Van Der Waals Forces
The model used to rationalize the existence of van der Waals forces begins with the assumption that during some very small instant of time the electron density in an atom can be unsymmetrically distributed in the same way that the electron density in a dipole is unevenly distributed. This uneven distribution perturbs the electron density in a neighboring atom through electrostatic repulsion of the electrons. The negative end of the induced dipole is attracted to the positive end of the instantaneous dipole (and vice versa) with the result that the atoms are attracted to one another.
The Dependence Of Capillarity On Hydrogen-Bonding
Capillarity, or the ability of a liquid to rise inside of a small diameter tube, is related to the attraction of the molecules for the surface of the glass walls. Molecules that capable of hydrogen-bonding are generally attracted strongly to the polar surface of glass. In this animation the relative rise of three liquids is shown. The two liquids on the right both have hydrogen-bonding. The ethyleneglycol on the far right has two hydroxyl groups per molecule and therefore has the greatest amount of hydrogen bonding. It moves the greatest distance up the capillary tube.
This animation is designed to show that in hydrogen bonding the hydrogen atom is directed toward a lone pair of electrons of a nearby molecule. Hydrogen bonding can occur between two molecules of the same compound, for example two ammonia molecules. It can also occur between two molecules of different compounds, for example, between a water molecule and a methanol molecule.