Young equation

The Young equation, named after scientist Thomas Young, relates the angle of contact between a liquid and a solid to the surface tensions of the liquid-air, liquid-solid, and solid-air interfaces. Surface tension is a measurable tension at the dividing surface between a liquid and its vapor, requiring work to increase the surface area. This phenomenon causes small liquid drops to form a sphere in the absence of gravity, as this shape minimizes surface area. Surface tension decreases with rising temperature and disappears at the critical point. It also exists between two immiscible liquids and between a liquid and a solid, though the latter is not directly measurable.1