What does specific gravity measure?

• A. The ratio of a material's density to air density
• B. The ratio of a material's density to water density
• C. The density of a material at varying temperatures
• D. The weight of a material compared to its volume

Answer: (B)

Specific gravity measures the ratio of a material's density to water density, which is a crucial concept in various fields, including hazardous materials handling and firefighting. This measurement is expressed as a dimensionless number, as it compares the density of a substance to the density of water at a standard temperature, typically 4°C (where water's density is approximately 1 g/cm³).

Understanding specific gravity is important because it helps determine whether a substance will float or sink in water. A specific gravity less than 1 indicates that the substance will float, while a value greater than 1 suggests it will sink. This is particularly relevant when dealing with hazardous materials, as knowing how a substance behaves in water can inform safety protocols and response strategies.

The other options, while related to density and material properties, do not accurately define specific gravity, which is strictly a comparison to water, rather than air or varying temperatures.