Question

Relative density, or specific gravity,[1][2] is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest (at 4 °C or 39.2 °F); for gases, the reference is air at room temperature (20 °C or 68 °F). The term "relative density" is often preferred in scientific usage.

Specific gravity
Common symbols
SG
SI unit
Unitless
Derivations from
other quantities
{\displaystyle SG_{\text{true}}={\frac {\rho _{\text{sample}}}{\rho _{\mathrm {H_{2}O} }}}}

A US Navy Aviation Boatswain's Mate tests the specific gravity of JP-5 fuel
If a substance's relative density is less than one then it is less dense than the reference; if greater than 1 then it is denser than the reference. If the relative density is exactly 1 then the densities are equal; that is, equal volumes of the two substances have the same mass. If the reference material is water, then a substance with a relative density (or specific gravity) less than 1 will float in water. For example, an ice cube, with a relative density of about 0.91, will float. A substance with a relative density greater than 1 will sink.

Temperature and pressure must be specified for both the sample and the reference. Pressure is nearly always 1 atm (101.325 kPa). Where it is not, it is more usual to specify the density directly. Temperatures for both sample and reference vary from industry to industry. In British brewing practice, the specific gravity, as specified above, is multiplied by 1000.[3] Specific gravity is commonly used in industry as a simple means of obtaining information about the concentration of solutions of various materials such as brines, sugar solutions (syrups, juices, honeys, brewers wort, must, etc.) and acids.

Basic calculation Edit
Relative density (RD) or specific gravity (SG) is a dimensionless quantity, as it is the ratio of either densities ​

Answer 1

Answer:

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