تسجيل الدخول

تسجيل

Density

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-149

2025-11-09

420

The quantity of matter, or the mass, in a unit volume measures the density of a substance. If a piece of lead, for example, has a mass of 45.4 g. and a volume of 4 cc., then the density of this lead equals 45.4÷4= 11.35 g. per cubic centimeter. The general expression is Hence, masses of equal volumes are directly proportional to their densities, and volumes of equal masses are inversely proportional to their densities.

Density=Mass/Volume

The relative density of a substance is the ratio of its density to the density of pure water at a temperature of 4°C. If we assume the quantity of matter in 1 cc. of pure water at 4°C. as a unit of density, the density of the water will be 1, and the quantity of matter in 1 cc. of any other substance will measure its relative density.

The density of water varies with its temperature as well as with its purity. The temperature 4°C. is taken for the standard density because the density of water is greatest at that temperature. In order to get the most accurate results in the following experiments, distilled water at 4° C. must be used.