Basic properties of liquids (continuum viewpoint): Which statement best characterizes liquids compared with solids and gases under ordinary conditions?

Introduction / Context:
Understanding the macroscopic properties of liquids is foundational for hydraulics, process engineering, and materials handling. These properties differentiate liquids from solids (rigidity) and gases (high compressibility and expansibility).

Given Data / Assumptions:

• Normal temperature and pressure, single-phase liquid.
• Continuum mechanics model (ignoring molecular-scale details).
• No phase change during observation.

Concept / Approach:

Liquids have very low compressibility, significant cohesion, and finite surface tension. They resist shear only transiently (flow under sustained shear) and thus do not maintain a fixed shape; instead they conform to the container, preserving essentially constant volume (neglecting slight compressibility).

Step-by-Step Solution:

Verification / Alternative check:

Everyday observation (water in a glass) and standard property tables (bulk modulus, thermal expansion coefficient) support the description.

Why Other Options Are Wrong:

(a) Incorrect—compressibility is small but not zero; (c) false—properties change with T and p; (d) false—liquids do not expand to fill any volume; (e) false—surface tension is finite in equilibrium.

Common Pitfalls:

Assuming “incompressible” means mathematically zero compressibility; conflating liquid behavior with gas behavior.

Final Answer:

Liquids do not retain a definite shape but assume the container’s shape