The physical characteristics of solids, distinct shape and volume was discussed using examples. The crystalline structure of crystal solids was demonstrated with microphotographs and actual microscopic slides. The concept of density as a ratio of mass/volume reviewed, with actual densities determined on a wood block and a metal block of the same dimensions. The affect of temperature and pressure on density was examined using ice and liquid water. The actual density of water was determined at the room temperature by measuring the mass of a given volume. The term specific gravity was related to the density of a substance compared to the density of water.