5. Liquids

5. Liquids

Concept Explanation:

Liquids have a definite volume but take the shape of their container. The particles in a liquid are close together, but they can move past each other, allowing the liquid to flow. Liquids have properties that are intermediate between solids and gases.

Key Properties of Liquids:
1. Surface Tension: A measure of the cohesive forces at the surface of a liquid, causing it to behave as if covered by a stretched elastic membrane.
2. Viscosity: A measure of a liquid's resistance to flow. Higher viscosity means the liquid flows more slowly (e.g., honey), while lower viscosity means it flows more easily (e.g., water).

Example Problem:

Explain how surface tension allows insects like water striders to walk on the surface of water.

Solution:

Surface tension arises because the molecules at the surface of a liquid experience a net inward force due to cohesive interactions with other molecules. This creates a 'skin' on the liquid's surface, which can support light objects. Water striders can walk on water because their legs distribute their weight over a large area, and the surface tension of the water is sufficient to support them without breaking the surface.