Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Intermolecular Forces: Surface Tension

In course

PHYS-108: General physics : fluids and electromagnetism

Le cours couvre deux grands chapitres de la physique: l'étude des fluides et l'électromagnétisme. Une introduction aux ondes est également faite pour pouvoir étudier les solutions des équations de l'hydrodynamique et des équations de Maxwell. ...

Description

This lecture covers the origin and definition of repulsion at short distances due to the Pauli principle, intermolecular interactions, and the role of tension in fluids. It explains the necessity of work to bring molecules to the surface, the behavior of liquid films, and the concept of surface tension. The lecture also discusses the analogy between liquid/gas interfaces and elastic membranes, the experimental determination of surface properties, and the consequences of minimizing surface area in soap bubbles. It concludes with demonstrations of objects floating on water due to surface tension and the movement of soap boats in different liquid environments.

This video is available exclusively on Mediaspace for a restricted audience. Please log in to MediaSpace to access it if you have the necessary permissions.

Watch on Mediaspace

Instructor

Christian Gabriel Theiler

Christian Theiler obtained his Master’s degree in physics from ETH Zurich in 2007 and his PhD from EPFL in 2011. He then joined MIT as a postdoctoral associate to work on the Alcator C-Mod tokamak. In 2014, he returned to EPFL as a EUROfusion fellow, to join the TCV tokamak team. Two years later, he was named Tenure Track Assistant Professor in Plasma Physics at EPFL. Christian’s research focuses on tokamak boundary physics and related diagnostic techniques. He has contributed to the understanding of the formation, propagation, and control of turbulent plasma structures, called blobs, and gained new insights on the structure of transport barriers in the plasma periphery in different high-confinement regimes. His current research focuses on detachment physics and turbulence characteristics in conventional and alternative divertor magnetic geometries.

Official source

Related concepts (32)

Liquid

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a nearly constant volume independent of pressure. It is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape. The density of a liquid is usually close to that of a solid, and much higher than that of a gas. Therefore, liquid and solid are both termed condensed matter.

Surface tension

Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play.

Liquid-mirror telescope

Liquid-mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury, but other liquids will work as well (for example, low-melting point alloys of gallium). The liquid and its container are rotated at a constant speed around a vertical axis, which causes the surface of the liquid to assume a paraboloidal shape. This parabolic reflector can serve as the primary mirror of a reflecting telescope.

Fluid mechanics

Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them. It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical, and biomedical engineering, as well as geophysics, oceanography, meteorology, astrophysics, and biology. It can be divided into fluid statics, the study of fluids at rest; and fluid dynamics, the study of the effect of forces on fluid motion.

Soap bubble

A soap bubble is an extremely thin film of soap or detergent and water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with another object. They are often used for children's enjoyment, but they are also used in artistic performances. Assembling many bubbles results in foam. When light shines onto a bubble it appears to change colour.

Related lectures (30)

Interfacial Chemistry: Introduction & Importance

Covers the basics of interfacial chemistry, including emulsions, surface tension, and the importance of interfaces in various applications.

Water: Properties and Importance

Explores the properties and significance of water, including its physical, electrical, and chemical characteristics, emphasizing its vital role in life and the environment.

Introduction to Fluid Mechanics

Covers the basics of fluid mechanics, including fluid properties, pressure, viscosity, and fluid behavior at rest and in motion.

Flash Drum: Principles and Mass Balance in Separation Processes

Covers the principles of flash drums and the mass and energy balances involved in separation processes.

Introduction to Fluid Mechanics: Basic Principles and Properties