Question

Glass and cement are two important examples of
A. man-made silicates
B. silicones
C. zeolites
D. organic polymers.

Answer 1

Hint: Cement is made from a mixture of elements that are found in natural materials such as limestone, clay and sand. Glass possesses no definite formula or crystalline structure. It is an inorganic product of fusion which has cooled to a rigid condition without crystallizing.

Complete step by step solution:
Glass can be made from different types of chemical compositions. These different types will make a change in its mechanical, chemical, optical, electrical, and thermal properties. There are three types of glasses-formers, fluxes, stabilizers. Glass is made up of silicon dioxide and sand. It is an amorphous, hard, brittle, transparent or translucent super cooled liquid of infinite viscosity. It is made by fusing a mixture of a number of metallic silicates or borates of sodium, potassium, calcium, lead.
Cement is a fine and soft powdery-type substance. It can bind sand and aggregates into a hard, solid mass called concrete when it binds with water. The relative proportions of the oxide compositions in cement are responsible for influencing the various properties of cement, in addition to rate of cooling and fineness of grinding.
The silicate mineral group is found in all the common rocks except limestone. Every silicate mineral contains oxygen and silicon.
Thus glass and cement are examples of man-made silicates.
Hence option A is correct.

Additional information:
Glass does not have a certain melting point. It softens over a temperature range. Silica as quartz, white sand and ignited flint are also used as raw materials for preparation of glass.

Note: Chemical components of cement are lime, silica, alumina, iron oxide, magnesia, alkalis, sulfur trioxide. An important ingredient which gives strength to cement is silica. If it is in excess, silica allows the cement to set slowly.