What is 'Specific Gravity'?

Specific gravity is defined as the ratio of the density of a substance to the density of a standard, typically water for liquids and air for gases. This measurement provides crucial context because it allows for the comparison of a material's density directly with that of the standard, providing insights into whether the substance will float or sink in water, as well as its relative heaviness.

In practical applications, understanding the specific gravity is essential, especially for industries involving liquids like heating oil. Different substances can have similar weights but varying densities; knowing specific gravity helps in identifying how they will behave under different conditions, including storage and usage in heating systems.

The concept does not directly pertain to buoyancy alone, which is a function of whether a body will float based on its specific gravity relative to water. While the other options mention weight, buoyancy, and density, they do not encapsulate the definition of specific gravity as clearly as the correct choice. This defined relationship between the densities illustrates why specific gravity is an important concept in fields such as chemistry and engineering.