# What is Density

You’ve probably heard of the density of a body before. Below you will learn how exactly this physical quantity is defined and how you can calculate it.

Density Definition

The density \varrhoϱ indicates how much mass mm a certain volume VV of a body has. So, the density is the ratio of mass to volume:

\varrho=\dfrac{m}{V}ϱ=

V

m

The density is expressed in the unit \frac{\pu{kg}}{\pu{m}^3}

m

3

kg

indicated. It is also possible to specify it in the unit \frac{\pu{g}}{\pu{cm}^3}

cm

3

g

.

You can convert between these units as follows:

1\,000\,\frac{\pu{kg}}{\pu{m}^3}=1\frac{\pu{g}}{\pu{cm}^3}1000

m

3

kg

=1

cm

3

g

.

Densities are often compared. With the density of water (1\,000\,\frac{\pu{kg}}{\pu{m}^3}1000

m

3

kg

) the density of other substances is compared to check whether they are buoyant. If a massive body has a higher density, it will sink in the water. If the density of the body is smaller, then it floats.

Density – examples from everyday life

The density of an average person, depending on how much air he inhales, is between 980\,\frac{\pu{kg}}{\pu{m}^3}980

m

3

kg

and 1\,020\,\frac{\pu{kg}}{\pu{m}^3}1020

m

3

kg

. This allows us to get on the water with a density of 1\,000\,\frac{\text{kg}}{\text{m}^3}1000

m

3

kg

to drift or to dive in this. If the density of the water is higher, as in the Dead Sea, it is even very difficult for us to sink.

But to float through the air like a helium balloon, our density is unfortunately much too high. Air has only a density of 1.2041\,\frac{\pu{kg}}{\pu{m}^3}1.2041

m

3

kg

. And helium has a density of just 0.1785\,\frac{\pu{kg}}{\pu{m}^3}0.1785

The density of liquids can be measured using density meters (hydrometers). It is used that there is a proportional relationship between the density of a liquid and the buoyancy force in it. There is also a proportional relationship between the buoyancy force and the immersed volume.

Thus, for a particular liquid, the following applies: the greater the depth of immersion of the hydrometer, the smaller the density of the liquid. The density can be read directly on the scale of the hydrometer.

What is a simple definition of density?

What is density full answer?

What is density and example?