Specific Gravity
Definition and meaning of Specific Gravity in chemistry.
Specific gravity is the calculated ratio of the density of a given substance to the density of a reference substance, typically water for liquids and solids.
In more detail
Because it is simply a ratio of two identical density units, specific gravity is a dimensionless quantity and has no physical units attached to it. A specific gravity value greater than one indicates that the substance is denser than water and will sink, while a value less than one means it is less dense and will float. This measurement is highly dependent on temperature, so the temperatures of both the sample and the reference material must be clearly specified for accurate reporting. It is widely used in industries like brewing, mineralogy, and medicine to characterize materials.
Key facts
| Field | General Chemistry |
|---|---|
| Units | Dimensionless (none) |
| Reference Material | Typically H2O at 4 degrees Celsius |
| Relation to Density | Ratio of densities |
The specific gravity of pure gold is 19.3, which means it is exactly 19.3 times denser than an equal volume of liquid water (H2O) at the same temperature.
Frequently asked questions
Is specific gravity the exact same thing as density?
No, density has physical units of mass per volume like grams per milliliter, while specific gravity is a unitless ratio comparing a substance's density to that of water.