How is density defined?

Density is defined as the weight per unit volume of a substance. This definition captures the relationship between mass and the space that an object occupies, indicating how tightly packed the matter within a substance is.

In practical terms, density is commonly expressed in units such as grams per cubic centimeter (g/cm³) or kilograms per liter (kg/L), which allows for clear comparisons between different materials. When you understand density in this manner, it becomes essential for various applications in fields like engineering and refrigeration, where knowing how materials interact under different conditions can influence system efficiency.

While other options hint at aspects related to density, they lack precision. For example, simply defining density as the weight of a substance compared to its volume doesn't accurately encapsulate the concept, as it overlooks the importance of specifying weight on a per volume basis. Similarly, stating that it is the ratio of mass to volume may imply a correct relation but does not communicate the specific emphasis on weight as part of the definition, which is pivotal in differentiating types of substances in various contexts. Therefore, understanding density as weight per unit volume provides the most comprehensive and accurate definition.