bulles

Bulles, known in English as bubbles, are discrete pockets of gas enclosed by a liquid film. They occur most commonly when gas is dispersed in a liquid, such as air bubbles in water, foam on a beverage, or carbonation in drinks.

Formation and stability: Bubbles form when gas comes out of solution or when a film traps gas during agitation. Nucleation sites, surface tension, and the presence of surfactants such as soaps influence a bubble’s size and longevity. Small bubbles are strongly affected by buoyancy and surface tension, while larger ones rise quickly and are more likely to burst at the surface.

Physical properties: The gas inside a bubble experiences the surrounding liquid pressure, and the film’s surface tension creates a pressure difference across the film (described by the Young-Laplace relation). Bubbles rise, deform, drain, and eventually rupture as the liquid film thins and drains.

Types and examples: Common bubbles include air bubbles in liquids, soap bubbles used in games and art, and carbon dioxide bubbles in beer and champagne. Cavitation bubbles arise from rapid pressure changes in liquids. In geology, gas vesicles form in magma and rocks. In medicine, microbubbles serve as contrast agents for ultrasound imaging.

Applications and significance: Bubbles are central to flotation processes in mineral processing, aeration in water treatment, and various chemical reactors. They have historically been used in physics as bubble chambers and detectors. In everyday life, they contribute to foams, culinary textures, and packaging materials such as bubble wrap.