Liquids are practically non-compressible because the molecules are already close together. Liquids exhibit a resistance to flow called viscosity . Viscosity and surface tension are related to the forces of attraction between molecules. This will be discussed later in this document. Properties of Solids Solids are even less compressible than liquids.
Solids retain both volume and shape.
Amorphous forms are rather unusual, although one of the most common examples of this form is ordinary glass. The crystalline form is by far the more common of the two. A crystalline solid exists in a regular, three-dimensional form called a crystal . Intermolecular Forces Substances which are gases have relatively weak forces of attraction between molecules. Remember that the weak forces are the cause for the gaseous state, not the effect of a substance being a gas.