What is the defining feature of liquids?

The defining feature of liquids lies in their flow properties, which are primarily due to the presence of weak secondary bonds among their molecules. In a liquid state, molecules are held together by these weaker interactions, allowing them to move past one another freely. This is why liquids can take the shape of their container while maintaining a definite volume. The fluidity and ability to flow are key characteristics that distinguish liquids from solids and gases.

In contrast, solids are characterized by strong bonds that hold their molecules tightly in a fixed arrangement, leaving no room for movement. Gases consist of randomly dispersed particles that have little to no interaction with one another, allowing them to spread out and fill a container completely. The solid state mentioned does not encompass the movement typical of liquids, making the description of flow properties due to weak secondary bonds the most accurate representation of liquids.