Glass

Glass is a uniform material of arguable phase (where the word "phase" is used to describe either a gas, liquid, or solid), usually produced when the viscous molten material cools very rapidly to below its glass transition temperature, without sufficient time for a regular crystal lattice to form. The most familiar form of glass is the silica-based material used for household objects such as light bulbs and windows. Glass is a biologically inactive material that can be formed into smooth and impervious surfaces. Under tension, glass is brittle and will break into sharp shards. Under compression, pure glass can withstand a great amount of force. The properties of glass can be modified or changed with the addition of other compounds or heat treatment.