What is a solid?

Physical Properties of Solids

The two types of solids are crystalline solids and amorphous solids.

Crystalline Solids

The atoms of crystalline solids are tightly bound together in a regular geometric pattern. These solids are rigid and resist changes in their shape or volume.

Crystalline solids can be represented by a chemical formula. For example, the quartz and citrine minerals in the photo are represented by the chemical formula SiO₂. Yes, both quartz and citrine have the same chemical formula. Impurities, such as manganese and iron and high temperatures give quartz a yellow color and it is called citrine.

Minerals, such as the cluster of quartz and citrine  are examples of crystalline solids.

While all crystalline solids have specific geometric shapes, large crystals are not always found naturally. This is because it takes space for crystals to grow and like the photo, other crystal solid growth gets in the way.

Amorphous Solids 

• The atoms of amorphous solids are tightly bound together but in no specific pattern. These solids can be rigid like glass, coal, and igneous rocks or flexible like rubber.  Plastics are amorphous solids. These solids can be formed by sudden cooling of liquids, such as volcanic lava.