Liquid bubble - AbsoluteAstronomy.com

A bubble is a globule of one substance in another, usually gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

in a liquid

Liquid

Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

.
Due to the Marangoni effect

Marangoni effect

The Marangoni effect is the mass transfer along an interface between two fluids due to surface tension gradient...

, bubbles may remain intact when they reach the surface of the immersive substance.

Common examples

Bubbles are seen in many places in everyday life, for example:

As spontaneous nucleation
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...

of supersaturated carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

in soft drink
Soft drink
A soft drink is a non-alcoholic beverage that typically contains water , a sweetener, and a flavoring agent...

s
As water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

in boiling water
As air mixed into agitated water, such as below a waterfall
As sea foam
Sea foam
Sea foam is a type of foam that appears in bodies of salt water. It can also refer to:*sponge toffee, a type of candy*A shade of the color green*A brand of fuel additive...
As given off in chemical reactions, e.g. baking soda + vinegar
As a gas trapped in glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

during its manufacture
An air bubble in a solution of fluorescein
Fluorescein
Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....

and water (or alcohol) is the essential part of a spirit level
Spirit level
A spirit level or bubble level is an instrument designed to indicate whether a surface ishorizontal or vertical . Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some...

Physics and chemistry

Bubbles form, and coalesce, into globular shapes, because those shapes are at a lower energy state. For the physics and chemistry behind it, see nucleation

Nucleation

Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...

Appearance

Humans can see bubbles because they have a different refractive index

Refractive index

In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

(IR) than the surrounding substance. For example, the IR of air is approximately 1.0003 and the IR of water is approximately 1.333. Snell's Law

Snell's law

In optics and physics, Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass...

describes how electromagnetic waves change direction at the interface between two mediums with different IR; thus bubbles can be identified from the accompanying refraction

Refraction

Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

and internal reflection even though both the immersed and immersing mediums are transparent.

The above explanation only holds for bubbles of one medium submerged in another medium (e.g. bubbles of air in a soft drink); the volume of a membrane bubble (e.g. soap bubble) will not distort light very much, and one can only see a membrane bubble due to thin-film diffraction and reflection

Reflection

Reflection or reflection may refer to:-Science:* Mirror image, a reflection in a mirror or in water* Reflection nebula, a nebula that is extended and has no boundaries* Reflection , a common wave phenomenon...

Applications

Nucleation can be intentionally induced, for example to create bubblegram

Bubblegram

A bubblegram is a 3D image composed of points suspended in a medium, typically a plastic block. It can be described as a 3D version of the late 19th century, European, 2D art of pointillism....

. In medical ultrasound

Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

imaging, small encapsulated bubbles called contrast agent are used to enhance the contrast. In thermal inkjet

Inkjet printer

An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...

printing, vapor bubbles are used as actuators. They are occasionally used in other microfluidics

Microfluidics

Microfluidics deals with the behavior, precise control and manipulation of fluids that are geometrically constrained to a small, typically sub-millimeter, scale.Typically, micro means one of the following features:* small volumes...

applications as actuators. The violent collapse of bubbles near solid surfaces and the resulting impinging jet constitute the mechanism used in ultrasonic cleaning. The same effect, but on a larger scale, is used in weapons such as the bazooka

Bazooka

Bazooka is the common name for a man-portable recoilless rocket antitank weapon, widely fielded by the U.S. Army. Also referred to as the "Stovepipe", the innovative bazooka was amongst the first-generation of rocket propelled anti-tank weapons used in infantry combat...

and the torpedo

Torpedo

The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

. Pistol shrimp also use the energy focusing of a collapsing cavitation bubble as a weapon. The same effect is used to treat kidney stones in a lithotripter. Marine mammals such as dolphins and whales use bubbles for entertainment or as hunting tools. Aerators cause dissolution of gas in the liquid by injecting bubbles.

Pulsation

When bubbles are disturbed, they pulsate (that is, they oscillate in size) at their natural frequency. Large bubbles (negligible surface tension

Surface tension

Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...

and thermal conductivity

Thermal conductivity

In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....

) undergo adiabatic pulsations, which means that no heat is transferred either from the liquid to the gas or vice versa. The natural frequency of such bubbles is determined by the equation:

where:

is the specific heat ratio
Heat capacity ratio
The heat capacity ratio or adiabatic index or ratio of specific heats, is the ratio of the heat capacity at constant pressure to heat capacity at constant volume . It is sometimes also known as the isentropic expansion factor and is denoted by \gamma or \kappa . The latter symbol kappa is...

of the gas
is the steady state
Steady state
A system in a steady state has numerous properties that are unchanging in time. This implies that for any property p of the system, the partial derivative with respect to time is zero:...

radius
is the steady state pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
is the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

of the surrounding liquid

Smaller bubbles undergo isothermal pulsations. The corresponding equation for small bubbles of surface tension σ (and negligible liquid viscosity

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

) is

Excited bubbles trapped underwater are the major source of liquid sound

Sound

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

s, such as when a rain

Rain

Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

droplet impacts a surface of water.

External links

Bubble physics – touches on vapor pressure, bubble formation, bubble dynamics, cavitation, acoustic oscillations, sound of raindrops underwater, Rayleigh-Plesset equation, snapping shrimp, lithotripsy, ultrasonic cleaning
Ultrasonic cleaning
thumb|300px|Ultrasonic cleaner showing the removable basket in place, and a closeup of the light and timerAn ultrasonic cleaner is a cleaning device that uses ultrasound and an appropriate cleaning solvent to clean delicate items...

, sonochemistry, sonoluminescence, medical reperfusion imaging, and micro-bubble therapy