Final answer:
The distinguishing physical characteristic between a fluid and a solid is the ability to flow. Solids are rigid with fixed shapes, while fluids can adjust their shapes to fit their containers due to lower intermolecular forces.
Step-by-step explanation:
Physical Characteristics of Fluids and Solids
The physical characteristic that distinguishes a fluid from a solid is the ability to flow. Solids maintain their shape because the atoms or molecules are in close proximity and the forces between these particles are strong, resisting deformation and shearing forces. In contrast, fluids, which include both liquids and gases, can adjust their shape to fit the container because their molecules are free to move relative to one another.
Answering the given question, the characteristic that distinguishes fluids from solids is their ability to flow. This is due to lower intermolecular forces, which allow the particles within a fluid to move past each other easily. Solids, on the other hand, have a fixed shape and high density and resist shearing forces, making them rigid.
As a practical example, water, which is a liquid, and air, which is a gas, can both flow and are considered fluids. On the other hand, materials like glass are solid at room temperature and do not flow.
Note: The density, melting point, boiling point, and flammability are examples of physical and chemical properties but are not the distinguishing factor between fluids and solids in terms of their ability to flow.