Capillary Pressure and Wettability Concepts

Interfacial tension is measured in units of dynes/cm.

The adhesion tension is defined as AT = σso − σsw.

A larger contact angle indicates a greater area wetted by oil.

The contact angle θ is unrelated to the adhesion tension.

In a vertical capillary tube, water is drawn up due to negative adhesion tension.

Wettability of the solid is influenced by the chemical properties of both the solid and the fluids.

A positive adhesion tension results in the liquid being drawn down in the capillary tube.

Interfacial tensions between fluids are irrelevant in the context of capillary pressure.

Capillary Pressure

Interfacial Tension: Defined as the force per unit length needed to create a new surface between two fluids, measured in dynes/cm, indicating specific surface energy.
Adhesion Tension: Describes the interaction between two immiscible fluids and a solid surface; given by the equation:
- σso = σsw + σwo cos θ
- Where σso represents the solid-fluid interfacial tension, σsw is the solid-water interfacial tension, σwo is the solid-oil interfacial tension, and θ is the contact angle.
Wettability and Contact Angle: The contact angle θ is pivotal in determining the wetted area by water versus oil on a solid surface. A smaller contact angle indicates a larger area is wetted by water, denoting a solid's preference for water (wettability).
Influence of Chemical Properties: The values of interfacial tensions, and consequently the contact angle and wettability, are impacted by the chemical properties of both the solid surface (mineralogy) and the fluids (oil and water).
Capillary Action: Illustrated by a vertical capillary tube submerged in water, where a water-wet glass surface leads to positive adhesion tension, causing the water to rise to a height (h) above the water level in the beaker.

This quiz explores the fundamental concepts of capillary pressure, interfacial tension, and wettability. It examines the influence of chemical properties on the behavior of immiscible fluids and their interactions with solid surfaces. Dive into the equations and principles that govern these important physical phenomena.