Question

Which of the following materials is hard, opaque and shines when freshly cut?
A.Rubber
B.Wood
C.Tin
D.Plastic

Answer 1

Hint: The shiny materials will be very clear and polished and it is very clean. Hence, this type of material will easily reflect the light. And in the case of hard materials, it can easily resist high pressure and temperature and it is very difficult to cut and we can’t reform into different shapes. And the opaque materials are not transparent. Hence, we can’t see through that material.

Complete answer:
The rubber is usually prepared by using organic materials and it is known as isoprene. And the rubber is not hard, opaque and shiny when freshly cut. Hence, option (A) is incorrect.
The wood contains the materials like carbon, hydrogen, oxygen and nitrogen etc. it has the properties like strength in compression, hardness, static bending etc. but, when it is cut, it will not shine. Hence, the option (B) is incorrect.
When the tin is freshly cut, it will shine and the tin is opaque and very hard. If the photons of light are passed through this object it will reflect into so many photons and it becomes very shiny.
Two allotropes are found in tin which is alpha-tin and beta-tin. The alpha tin is a semi metallic form and it is dull, brittle and powdery. But the beta tin is very shiny and it is a metallic form. Hence, option (C) is correct.
Plastic is a little hard and opaque material. But when it is cut, it will not shine. Hence, the option (D) is incorrect.

Note:
Among these options, tin is very hard and opaque. And when it is cut, the material will shine. The tin is highly crystalline and ductile material. And the tin is opaque in nature. Because, it will not allow the light to pass through that material. But in the case of the other three materials, which will not shine after being cut. And it is not harder than tin.