Density is the measure of the mass present per unit volume of a substance. Density helps us to understand how mass is distributed within a substance. Relative density helps us to understand the density in comparison to the density of a standard material. Relative density is useful in comparing two substances in terms of density with respect to a standard. In this article, we discuss the 10 differences between density and relative density.
Difference between density and relative density
| Parameters | Density | Relative density |
| Definition | Density is the ratio between the mass and the volume of a body. | Relative density is the ratio of the density of the material to the density of a standard reference at a particular temperature. |
| Unit | Grams per cubic centimeter. | No unit. |
| Meaning | It Tells us how mass is distributed within the material | Helps us to compare the density of materials with respect to a standard. |
| Characteristic | Density is a constant characteristic of a body. They are different in different bodies. | The relative density of a material can be of different values depending on the reference used. |
| Factors affecting | The density of a substance is influenced by its shape, temperature, composition, physical state, electric field, etc. | The relative density is influenced by the temperature, pressure, and nature of the substance. |
| How they are calculated? | The formula for density is the mass of an object divided by its volume. In equation form, d = m/v where, •d is the density, •m is the mass •v is the volume of the object. | The formula of relative density is given as : Relative density = Mass of a substance of any volume/ mass of an equal volume of water at 4°C. |
| Applications | Density is applied in various areas like: • Oil spills. •ships and submarines •Plumbing systems •Airplane weight distribution •In Archimedes principle •Positive, neutral and negative Buoyancy. | Relative density is required in different areas such as •Relative density can be used to calculate the density of an unknown substance from a known standard substance. •It is used by geologists to find out the mineral content of the rock. •Testing the purity of a substance. |
| Measurement | A hydrometer is used to determine the density of liquids. | There are different methods to calculate the relative density, such as: •Buoyancy methods. •Hydrometer. •Hydrostatic balance. •Immersed body method. •Pycnometer Method. •Air comparison Pycnometer method for solids. •Oscillating densitometer. |
| Examples | •The density of water decreases as temperature decreases, so ice floats on water. •Helium balloons float in air due to very low density | •For testing the purity of substances such as gold, silver, etc by comparing it with pure reference. |
| Images |  A very highly dense atomic packing. |  The relative density of ice(w.r.t water) is less than 1 hence it floats on water. |
How can the difference between density and relative density be visualized in real life?
Suppose you are driving on a road and see dense traffic. You would definitely prefer a road that is relatively less dense, and you take a second road. So we say that the second road is less dense than the first road. But the density of both the roads can be measured as 25 cars/m and 10 cars/m or something.
Another example to show the difference between density and relative density in real life would be forests. When the trees in a forest are very closely planted together we say it is a dense forest. And when we see a farm where trees are spaced relatively far we say this is relatively less dense. But the fact is both have a density corresponding to the respective units.
What are the differences in the application of density and relative density?
Density is used in various day-to-day applications like building a ship or submarine, it is used to determine whether a ship will float or not, oil spills and ice float on water due to the difference in density, flight of an airplane, fluid motion lamps, etc. Relative density, on the other hand, is useful in determining the density of unknown substances, quantitatively determining the number of minerals in a rock, and also determining the purity of the material, and the famous phenomenon of ice floating on water is due to the relative density.
