Question

Which of the following substances has the lowest specific gravity?
A. Iron
B. Gold
C. Marble
D. Brass

Answer 1

Specific gravity is also known as relative density, it is defined as the ratio of the density of the substance to that of the standard. The standard used for solids and liquids is water at four degrees Celsius. Gases are compared with the dry air at zero degrees Celsius and one standard atmosphere.

Complete step by step answer:
Iron, gold, and brass being metallic in nature, are very strong and have a higher relative density in comparison to marble. If you think practically, you can not iron, gold and brass in a blow of hammer but in the case of marble, it can be done if the blow is strong enough. This gives an idea of how dense these substances are.

Talking about numbers, the specific gravity of iron is $7.87\,g/c{m^3}$ , the specific gravity of gold is $19.32\,g/c{m^3}$ , the specific gravity of brass is $8.73\,g/c{m^3}$ , and the specific gravity of marble ranges from $\;2.52\,g/c{m^3}$ to $2.64\,g/c{m^3}$. Hence, from the reported values of the specific density gold has the highest specific density, and marble has the lowest specific density among the given options.

Hence, the correct answer is C.

Note: Specific gravity is the basis of the method used to concentrate ore in history.Panning, jigging, shaking, spiral separation, and heavy medium separation are some methods that rely on differences in specific gravity to obtain concentrates. The specific gravity is the highest among the rocks rich in iron, magnesium oxide, and heavy metals, and the lowest among the rocks rich in alkali, silicic acid, and water.