Materials and Their Applications

Gunpowder (black powder) is a historical explosive mixture composed of sulfur (S), charcoal (C), and potassium nitrate (KNO3) in specific ratios. This composition has been used for centuries in firearms and fireworks. Cement is made from limestone and clay, while glass is primarily silica-based.

Cork is an excellent material for making bottle stoppers because it is airtight.

This is the correct option. The friction produced will be maximum if one rubs sand paper on another sand paper because both the surfaces are rough and on rough surfaces, friction is maximum.

The students may conclude that gamma rays have maximum penetrating power, and therefore, they are used to control the thickness of paper, plastic and metallic sheets during their manufacture.

Mylar is a polyester film that was used as the base material for floppy disks, coated with magnetic material on both sides. This material provided the necessary flexibility and durability. Option C correctly identifies Mylar. Note: option text has leading space before 'Mylar'.

CaCO₃ is used as a building material in the form of marble.

Among the given minerals topaz is the hardest. Hence, resistant to being scartched.

Crooks’ glass is a special type of glass containing cerium oxide. It does not allow the passage of ultraviolet rays and used for making lenses.

Silica fibres made of sodium silicate (water glass) are used in heat protection (including asbestos substitution) and in packings and compensators. They can be made such that they are substantially free from non-alkali metal compounds.

Glass wool, which is commonly known as fiberglass today was invented in 1938 by Russell Games Slayter of Owens-Corning as a material to be used as insulation.

Steel is the most elastic material among the options. Elasticity is defined as the ability to return to original shape after deformation. Steel can undergo significant elastic deformation before permanent deformation occurs, making it highly elastic.