Certified Fire Investigator Practice Exam

How is the "Specific Gravity of a Liquid or a Solid" defined?

1. As the weight of liquid compared to its vapor

2. The mass of a substance compared to air

3. The ratio of mass of a given volume of a substance to that of an equal volume of water

4. The measure of density at room temperature

The correct answer is: The ratio of mass of a given volume of a substance to that of an equal volume of water

The definition of "Specific Gravity of a Liquid or a Solid" refers to the ratio of the mass of a given volume of a substance to that of an equal volume of water. This relationship is crucial because it allows for the comparison of densities between different materials relative to water, which has a specific gravity of 1.0 at standard temperature and pressure. When measuring specific gravity, if a substance has a specific gravity less than 1, it is lighter than water and will float. Conversely, if it is greater than 1, the substance is denser than water and will sink. This concept is essential in fields such as fire investigation, where understanding the behavior of materials in different conditions is critical for assessing fire dynamics and the properties of combustibles. Other options present definitions that do not accurately capture the essence of specific gravity. For instance, focusing on the weight of a liquid compared to its vapor does not provide a proportional relationship in terms of volume with water. Similarly, comparing the mass of a substance to air is a different calculation known as density, not specific gravity. Lastly, measuring density at room temperature does not specifically define specific gravity, as it could vary with temperature and does not make the direct comparison to water succinctly. Overall,