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Related Concept Videos

Surface Tension, Capillary Action, and Viscosity02:57

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
Surface Tension of Fluid01:22

Surface Tension of Fluid

Surface tension is a fundamental property of fluids, occurring at the boundary between a liquid and a gas or between two immiscible liquids. This phenomenon arises from the cohesive forces between molecules at the fluid's surface, creating an effect similar to a stretched elastic membrane. Inside each fluid, molecules are equally attracted in all directions by neighboring molecules, but surface molecules experience a net inward force, resulting in surface tension.
Surface tension varies with...
Surface Tension and Surface Energy01:16

Surface Tension and Surface Energy

When a paint brush is immersed in water, the bristles wave freely inside the water. When it is taken out, the bristles stick together. The reason behind this effect is surface tension.
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
Surface Tension01:24

Surface Tension

Surface tension is defined as the force per unit length (γ) acting along the surface of a liquid. It arises due to strong intermolecular forces of attraction. A molecule located inside the bulk of the liquid is surrounded by other molecules and experiences equal forces in all directions. However, a molecule at the surface experiences unbalanced forces because there are more neighboring molecules below than above. This creates a net inward force that pulls surface molecules toward the interior,...
Excess Pressure Inside a Drop and a Bubble01:13

Excess Pressure Inside a Drop and a Bubble

The shape of a small drop of liquid can be considered spherical, neglecting the effect of gravity. This drop can further be considered as two equal hemispherical drops put together due to surface tension. The forces acting on the spherical drop are due to the pressure of the liquid inside the drop, the pressure due to air outside the drop, and the force due to the surface tension acting on the two hemispherical drops.
Pressure of Fluids01:14

Pressure of Fluids

There are many examples of pressure in fluids in everyday life, such as in relation to blood (high or low blood pressure) and in relation to weather (high- and low-pressure weather systems). A given force can have a significantly different effect, depending on the area over which the force is exerted. For instance, a force applied to an area of 1 mm2 has a pressure that is 100 times greater than the same force applied to an area of 1 cm2. That's why a sharp needle is able to poke through skin...

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Updated: Jul 11, 2026

Accurate Determination of the Equilibrium Surface Tension Values with Area Perturbation Tests
07:57

Accurate Determination of the Equilibrium Surface Tension Values with Area Perturbation Tests

Published on: August 30, 2019

Forces between surfaces in liquids.

J N Israelachvili, P M McGuiggan

    Science (New York, N.Y.)
    |August 12, 1988
    PubMed
    Summary
    This summary is machine-generated.

    Direct measurements of forces between surfaces in liquids reveal diverse interactions. Understanding hydration and hydrophobic forces at the ångstrom level remains a key challenge for physics and chemistry.

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    Area of Science:

    • Surface science
    • Physical chemistry
    • Nanotechnology

    Background:

    • Direct force measurements between surfaces in liquids are crucial for understanding interfacial phenomena.
    • Ångstrom-level resolution provides unprecedented detail into surface interactions.
    • Complex systems in biology and technology rely on understanding these forces.

    Purpose of the Study:

    • To review recent advancements in direct force measurements between surfaces in liquids.
    • To highlight the insights gained into liquid structure and interactions at surfaces.
    • To identify fundamental interactions, like hydration and hydrophobic forces, that require further investigation.

    Main Methods:

    • Direct force measurements at ångstrom resolution.
    • Analysis of interaction potentials based on surface and liquid properties.
    • Review of experimental and theoretical approaches.

    Main Results:

    • Observed a wide range of interactions and potentials dependent on surface and liquid characteristics.
    • Gained new insights into the structure of liquids adjacent to surfaces.
    • Identified hydration and hydrophobic forces as areas needing further study.

    Conclusions:

    • Direct force measurements offer valuable insights into interfacial phenomena.
    • The fundamental origins of hydration and hydrophobic forces remain poorly understood.
    • Further experimental and theoretical work is needed to elucidate these critical interactions.