Materials and Their Applications

Being fairly chemically inert, relatively non-toxic, and white, alumina is a favoured filler for plastics. Alumina is a common ingredient in sunscreen.

Quartzite ballast is best suited for steel sleepers because of its high hardness, angular particle shape, and excellent interlocking properties. Steel sleepers can crush softer ballast materials like sand or gravel, but quartzite maintains its integrity and provides stable support even under steel sleeper loads.

Shale is used in making bricks, tiles, pottery, chemical ware, furnace linings and lightweight concrete aggregates.

Nichrome is an alloy of nickel and chromium that is both hard and ductile, making it useful for heating elements. Carborundum is extremely hard but brittle. Tungsten is very hard but has limited ductility at room temperature. Cast iron is hard but brittle.

Radioactive element is not a household waste.

Forks, drivers (screwdrivers), and knives are typically made of steel, which is a magnetic material because it contains iron. Steel is ferromagnetic, meaning it's attracted to magnets and can be magnetized itself. Insulators like plastic or rubber don't conduct electricity, transparent materials allow light through, and non-magnetic materials wouldn't be attracted to magnets - but steel utensils are magnetic.

 Both the plastic fork and the glass rod will get charged upon rubbing with the flannel and silk cloth. Thus, they will be able to attract the pieces of paper.

Ice will melt least in wooden box. It is because wood is a poor conductor of heat which does not allow heat to pass through them easily.

Diamond is used for protective windows in space probes because of its exceptional hardness, thermal conductivity, and transparency to a wide range of electromagnetic radiation. Diamond can withstand extreme conditions, micrometeoroid impacts, and radiation while maintaining optical clarity.

Silicon carbide (SiC) is one of the hardest synthetic materials, ranking just below diamond on the Mohs scale. It's extensively used as an abrasive for cutting and polishing very hard substances like glass, ceramics, and other carbides. The other options don't match SiC's primary applications.

Rubber, wood and metal are the objects which do  not allow light to pass through then at all and nothing can be see through these objects. Whereas glass sheet is a transparent object as it allows light to pass through it.

So, it is water which is transparent in nature whereas iron, table and cloth are all examples of opaque materials.

Plastics are bad conductors of heat. So, they are used for the said purpose.

Glass is primarily made from sand (silica) and silicates (option C). The main ingredient in glass production is silicon dioxide (SiO2) found in sand, combined with various silicate compounds. Option A is incorrect because quartz is a form of silica itself, not combined with mica. Option B is incorrect because salt is not a standard glass ingredient.

Pyrex glass, also known as borosilicate glass, is highly heat-resistant due to its boron oxide content. This property makes it ideal for laboratory equipment and kitchenware. Other glass types like hard glass, flint glass, and bottle glass lack this specialized heat resistance.