What does specific gravity describe?

Specific gravity is a measure that describes the relative density of a substance compared to the density of water. Specifically, it is defined as the ratio of the weight of a given volume of a liquid to the weight of an equal volume of water at a specified temperature, typically at 4 degrees Celsius where water is at its maximum density.

This measure is crucial for understanding how a substance will behave in different environments, especially concerning whether it will float or sink in water. A specific gravity less than 1 indicates that the substance will float, while a value greater than 1 means it will sink in water. Being able to determine a substance's specific gravity is essential in hazardous materials management, as it aids responders in assessing potential risks and planning appropriate responses in a spill or leak scenario.

The other options do not accurately define specific gravity: the density of solid materials is a broader concept that doesn't pertain specifically to the comparison to water; volatility relates to how a substance vaporizes; and the ignition temperature describes the flammability of a material rather than its density.