How is density defined in relation to a substance?

Density is defined as mass per unit volume, which means that it quantifies how much mass is contained in a given volume of a substance. Specifically, it can be expressed mathematically as:

[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} ]

This relationship is fundamental in chemistry and physics because it helps to understand how substances behave under different conditions, including temperature and pressure. For example, a substance with a high density will have more mass packed into a smaller volume compared to a substance with a low density.

Understanding density is crucial for various applications, such as determining whether an object will float or sink in a fluid, as well as in calculations involving mixtures and solutions. In practical scenarios, if you know the density of a substance, you can easily calculate how much mass is present in a specific volume or vice versa, which is essential for laboratory work and industrial processes.

The other options provided do not accurately reflect the definition of density; they either describe different relationships or physical properties that do not pertain to density specifically.