What is the Difference Between Bulk Density and Specific Gravity

The key difference between bulk density and specific gravity is that bulk density is a direct measurement, whereas specific gravity is a relative value.

Density is the mass per unit volume of a substance. Specific gravity or relative density is the ratio between the density of a substance to the density of a given references material.

1. Overview and Key Difference
2. What is Bulk Density
3. What is Specific Gravity
4. Bulk Density vs Specific Gravity in Tabular Form
5. Summary – Bulk Density vs Specific Gravity

What is Bulk Density?

Density is the mass per unit volume of a substance. Density is an important characteristic of matter. It is directly connected to mass. Therefore, getting a clear understanding of it is vital to have a clear understanding of mass. Accordingly, mass is a measurement of the inertia of an object.

For a bulk material with uniform mass distribution, we can easily calculate this parameter by dividing the total mass of the object by the total volume occupied. However, if the mass distribution is not even, we need more complicated methods to measure the density.

Furthermore, we can easily describe the floatation of a substance using its density. Here, floatation means that a fluid or a uniform solid that is denser than a given fluid will drown in the given fluid. Thus, if the density of the fluid or the uniform solid is lesser than that of the given fluid, it will float on the given fluid. Moreover, we can define the term relative density in order to compare the densities of the two fluids. This is the ratio of the two densities and is merely a number.

What is Specific Gravity?

Specific gravity or relative density is the ratio between the density of a substance to the density of a given references material. For liquids, specific gravity is usually always measured with respect to that of water at its densest state. When considering gases, we can measure them using air as a reference at room temperature. In scientific use, the term relative density is used more often than the term specific gravity.

For a particular substance, if the specific gravity is less than 1, it tends to float on water if we use water as the reference material. e.g., ice cube float on water. In contrast, if the specific gravity is higher than 1, the substance will sink in water.

However, when measuring the specific gravity of a substance, the temperature and pressure must be indicated because it depends on these two factors. For example, pressure is nearly always 1 atm, and temperatures for both sample and reference are specific for different industries.

What is the Difference Between Bulk Density and Specific Gravity?

Density is the mass per unit volume of a substance. Specific gravity or relative density is the ratio between the density of a substance to the density of a given references material. The key difference between bulk density and specific gravity is that bulk density is a direct measurement whereas specific gravity is a relative value. Therefore, specific gravity has no no unit of measurement while the unit of measurement of bulk density is gcm^-3.

The below infographic presents the differences between bulk density and specific gravity in tabular form for side by side comparison.

Summary – Bulk Density vs Specific Gravity

Bulk density or generally, density and specific gravity are very important terms in different industrial applications. The key difference between bulk density and specific gravity is that bulk density is a direct measurement, whereas specific gravity is a relative value.