Hardness Of Solids:

Some solids are really "more solid" than others. The quantitative means of stating hardness, termed as the Mohs scale, categorizes solids from 1 to 10. The lower numbers symbolize softer solids, and the higher numbers symbolize harder ones. The standard substances used in the Mohs scale, all along with their hardness numbers, are shown in the table below. The test of hardness is easy and dual: (1) a substance forever scratches something less hard than itself, and (2) a substance not at all scratches anything harder than itself.

An illustration of a soft solid is talc that can be crumbled in the hand. Chalk is the other soft solid. The wood is somewhat harder than either of these. Limestone is harder still. After that, in increasing order of hardness, there are quartz, glass, and diamond. The hardness of a solid forever can be determined according to which samples scratch the other samples.

Most of the substances have hardness numbers which change with temperature. In common, colder temperatures harden these materials. Ice is a good illustration. It is a quite soft solid on a skating rink, though on the surface of Charon, the sulkily cold moon of the planet Pluto, ice water is as hard as granite.

Hardness is measured by sustaining laboratory samples of each of the 10 substances noted in the table shown below. A scratch should be a unending mark, not just a set of particles relocated from one substance to other. Substances generally have hardness values which fall between two whole numbers on the scale. The Mohs hardness scale is not particularly precise, and many scientists desire more detailed methods of defining and measuring the hardness.

Table: The Mohs Scale of Hardness (Higher numbers symbolize harder substances. Relative hardness is determined by effecting to scratch one substance with the other.)