In the solid state most atoms, ions and molecules are confined in more or less regular 3-dimensional structures which are called lattices

. Crystalline solids fit this description and most solids are crystalline. Amorphous solids (such as glass) have little local structure and the atoms or molecules of such solids are "arranged" more like a very viscous liquid.

With either type of solid, the particles are restricted greatly in motion. Energy absorbed as the temperature is raised goes into small vibrations of the particles in the vicinity of the lattice points . The rigidity of the crystal structure will thus be related to the entropy of the solid at different temperatures since little energy can be dispersed by such small movements and so we find that harder solids tend to have lower entropies. The specifc heats of very hard solids also tend to be low because of the limited ways in which heat energy can be dispersed as particle motion.