TeXes Science Practice Test

What chemical compound primarily constitutes the structure of window glass?

1. CaCl

2. HCl

3. SiO2

4. H2CO3

The correct answer is: SiO2

The primary component of window glass is silicon dioxide, which is represented by the chemical formula SiO2. This compound is the result of silicon and oxygen forming a strong bond that creates a rigid structure. In nature, SiO2 commonly occurs as quartz and is abundant in various minerals. Silicon dioxide is favored in glassmaking due to its favorable properties, which include transparency, chemical stability, and thermal resistance. When heated to high temperatures, silica can be melted and then cooled to form glass without crystallizing, leading to the smooth, clear material used for windows and other glass products. Other compounds mentioned, such as calcium chloride (CaCl), hydrochloric acid (HCl), and carbonic acid (H2CO3), do not constitute the structural base of glass. They serve entirely different purposes and lack the necessary properties for glass production. Thus, silicon dioxide's unique qualities make it the key component in the formation of window glass.