What is the term for the ratio of the weight of a given volume of a liquid compared with the weight of an equal volume of water?

The correct term for the ratio of the weight of a given volume of a liquid compared to the weight of an equal volume of water is "specific gravity." This concept is important in various fields, including firefighting, as understanding the specific gravity of liquids can influence how they interact with water, which is crucial for fire suppression efforts.

Specific gravity provides a dimensionless number that helps determine whether a liquid will sink or float when mixed with water. For instance, a liquid with a specific gravity greater than 1 will sink in water, while a liquid with a specific gravity less than 1 will float. This characteristic aids in making decisions about which extinguishing agents to use in various fire situations, especially when dealing with flammable liquids.

Other terms such as specific heat, densitometry, and viscosity refer to different physical properties of substances and do not relate to this particular ratio. Specific heat involves the amount of heat required to change the temperature of a unit mass of substance, densitometry is the measurement of the density of substances, and viscosity describes a liquid's resistance to flow. Understanding these distinct terms is important but does not help in identifying the specific definition of specific gravity as the correct choice.