I notice, sometimes this happens more than others. The bubbles form as air is entrained in the water during the pouring process. The key factor here is how fast the bubbles collapse. This may seem a funny distinction, but bubbles are always thermodynamically unstable compared to the bulk liquid because it always costs energy to create them. The only reason we see long lived bubbles is that there is a kinetic barrier that stops the water films collapsing.
This image shows schematically what the water film in a bubble looks like this is a soap bubble but the principle applies to all bubbles :. The water contains a chemical soap in this case that is surface active i. In the case of soap the end that sticks into the water the red blob in the picture is negatively charged and the negative charges on the opposite sides of the water film repel each and stop the film from thinning and collapsing.
In your case you say there's no soap suds present , though note that there may be very small amounts of surfactant present, even on apparently clean glass, because surfactant adsorbs on glass and it can be difficult to wash it all off. However lots of other things are surface active including many biopolymers, and your glass may have traces of some polymer. Absolutely clean water in an absolutely clean glass will not form a stable foam, so in your case there must be some contaminent present, either on the glass or in the tap water.
Rick Watling, a meteorologist with the National Oceanic and Atmospheric Administration, offers this explanation. Atmospheric gases such as nitrogen and oxygen can dissolve in water. Colder water and higher pressure allow more gas to dissolve; conversely, warmer water and lower pressure allow less gas to dissolve. When you draw a glass of cold water from your faucet and allow it to warm to room temperature, nitrogen and oxygen slowly come out of solution, with tiny bubbles forming and coalescing at sites of microscopic imperfections on the glass.
Hence bubbles along the insides of your water glass. Stone, Gareth H. McKinley, Ruben Juanes. Restoring universality to the pinch-off of a bubble. ScienceDaily, 17 June Massachusetts Institute of Technology. Mystery of how gas bubbles form in liquid solved.
Retrieved November 10, from www. As the bubbles burst, the released carbon dioxide gas imparts the beverage's desirable tang. Optical cavitation uses a laser to form bubbles in a liquid that expand rapidly then collapse. The customizable, 'wet' foams are intended for The strain and curvature introduced by the bubbles is known to tune ScienceDaily shares links with sites in the TrendMD network and earns revenue from third-party advertisers, where indicated.
Print Email Share. We use a scheme given in Fig. Percolating through pores, air enters the water in the form of thin air jets whose radii are comparable with the diameter of the pores. In water near the interface with a porous material, each jet breaks up into air bubbles due to the Rayleigh—Plesset [ 14 , 15 ] instability. Then the newly-formed bubbles grow according to the scheme 14 , as illustrated schematically in Fig.
In the first stage of evolution, bubbles spread over a distance of the order of the tube radius, and at this stage of bubble evolution, the total number density of air molecules in bubbles is of the order of the number density of molecules in atmospheric air. In the second stage of evolution, bubbles formed in the first stage spread throughout the water volume. As a result, the rate of bubble generation matches the rate of the floating up process for bubbles, including accounting for their growth due to the coagulation process.
Scheme of injection of submicron air bubbles into water: 1 container, 2 water, 3 flux of air bubbles, 4 porous material, 5 compressed air, 6 valve, 7 plunger, 8 region of high air density. In order to understand the real character of bubble evolution, we evaluate parameters of this evolution under conditions of experiment [ 3 ].
The flow velocity V varies in the experiment [ 3 ] from 0. From this we find that the rate of insertion of air molecules into water through a porous material is. The number density of air molecules in bubbles near the entrance into the water is given by.
As we discussed above, we divide the evolution of bubbles in water into two stages. In the first stage, the flow of water forming bubbles does not include new water additions, i. In the second stage of bubble evolution, they mix with water in the container.
This leads to a decrease in the total number density of air molecules in the container, and we assume that bubbles mix with water of the container uniformly.
We assume that the number density of air molecules in bubbles does not vary so long as the flowing bubbles do not encounter container walls. This yields an average bubble radius from 0. Correspondingly, the average number density N w of air molecules in bubbles over all the container is. As bubbles evolve in a water reservoir, they grow by coagulation and leave when they reach the water-air boundary. But because motion of water has a turbulent character under experimental conditions [ 3 ], departure of bubbles is determined primarily by parameters of turbulent motion, rather than simply by the rate of the smooth floating up of bubbles.
In considering the above regime of the kinetics of bubbles of micron and submicron size, we were guided by experimental conditions [ 3 ] in which a gas is injected into a liquid through a porous material with nano-size pores. There, the gas enters the liquid in the form of jets whose radii correspond to pore sizes, and then the jets are destroyed due to the Rayleigh—Plesset instability [ 14 , 15 ] and transform into micron-size bubbles which then join to bubbles of larger sizes.
In particular, within the framework of experiment [ 3 ], bubbles that form in water after association of injected bubbles contain a few of hundreds of the initially injected bubbles. Let us consider one more example, in which bubbles propagate along a tube in a liquid flow.
In this example we will be guided by the blood flow [ 16 — 18 ]. It should be noted that if contrast agents or drugs are injected in blood, they dissolve in blood water, and just this mixture is used in clinical applications [ 19 — 21 ]. Therefore an injected medicine must not react with walls of a blood vessel in this case.
In the case under consideration an injected substance may react with a blood vessel, and it is necessary to transport the medicine through a blood vessel without contacts with walls. Let us inject this medicine in the center of a blood flow in the form of micron-size bubbles or droplets and they travel over the vessel cross section as a result of diffusion or floating-up.
For example, these bubbles may contain ozone or another oxidizer, and these substances lose chemical activity if bubbles contact the walls of a blood vessel. Below we determine the lifetime of bubbles in a blood flow under these conditions.
Comparing the propagation of a bubble in water due to floating-up and diffusion, one obtains that transport due to floating-up takes place for distances L. Hence, the floating-up mechanism is realized for bubble transport of micron-size bubbles through a blood vessel. If this criterion holds true, the bubble displacement in blood flow through a venous duct is small compared with its radius.
Along with this criterion, there is a requirement of a restricted number density of bubbles, so that a doubling time of a bubble size as a result of their association must exceed their residence time in the flow. In addition, one can take instead of bubbles micron-size droplets. These bubbles and droplets may be used not only for transport of some substances through a blood vessel, but they can be catalysts to remove harmful compounds from the blood.
Above we analyze conditions where transport of bubbles through a blood vessel excludes their interaction with vessel walls. Another problem of their interaction with red corpuscules will require a special analysis of its own. Disperse systems under consideration consist of a liquid and gaseous bubbles. If a gas is inserted into a liquid and its amount exceeds the maximum level of solubility of that gas, the excess gas forms bubbles in the liquid through time.
Processes in such a system with micron-size bubbles include diffusion and floating-up of bubbles, as well as association of contacting bubbles. The above rates of these processes allow us to describe the kinetics of growth for a disperse system of such a type. We consider disperse systems located in a container with an open surface containing the gas above the interface. Because of the long time of bubble floating-up under laboratory conditions, bubbles grow in the liquid and their size is independent of initial conditions when they reach the interface.
This fact simplifies the problem and allows us to connect a size of floating-up bubbles with the gas concentration in the liquid and the path to the interface. The above analysis allows one to choose optimal conditions for any process involving micron-size bubbles or droplets for a certain disperse system.
In analyzing the behavior of a gas inside a liquid, we show that thermodynamic equilibrium in this system takes place between dissolved molecules and the liquid, while excess molecules leave the liquid. In the regime under consideration an outgoing time is relatively long, and the number density of dissolved molecules is small compared to undissolved ones, and this gas-liquid system is a nonequilibrium one. In the end, undissolved molecules leave the liquid through its boundary, and most of the time in the course of this process, undissolved molecules are in the liquid in the form of bubbles.
Then the rate of exit of undissolved gas molecules in the liquid is summed from kinetics of bubble growth as a result of their association and floating up under the action of the gravitation force. We use here the classical theory of growth kinetics of aerosols in a gas [ 8 — 10 ] which is constructed on the basis of the Smoluchowski equation [ 6 ] and was applied to growth of liquid clusters in a gas [ 11 , 12 ] in the diffusion regime of the cluster growth process.
Using the analogy of the above growth processes with bubble growth in a liquid, we apply formulas for kinetics of aerosol and cluster growth in this case. As a bubble grows, its floating velocity increases, and accounting for both processes allows us to determine the bubble life time in a liquid with an open upper surface.
The evaluations are made for the growth and floating up of the oxygen bubbles in water. This process takes place when oxygen results for the photosysntesis process in a water reservoir. It should be noted that this model may be used also for the analysis of bubble evolution of liquid flows if they propagate through a tube. This may be used for injection of drugs or contrast agents in blood that propagates through a blood vessel [ 16 — 18 ].
In such applications, usually the injected substance is mixed with a blood or is dissolved in it [ 19 — 21 ]. The above approach allows one to deliver a substance in the form of bubbles or droplets, and the above theory gives conditions to escape interaction of injected bubbles with vessel walls. This provides a list of possible medical applications. BMS was the initiator of this study.
Both authors read and approved the final manuscript. Boris M. Smirnov, Email: moc.
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