Gas generation

[einsteinsdog]

When you observe fizzy liquid in a glass the bubble almost invariably come from the bottom of the glass.

Now boyles law and charles law I have no problem with but this is crazy . The bubbles should come from the top or sides not the bottom as the pressure is considerably higher on the bottom!

This fizzy is contravening the laws of science .Does your fizzy behave the same way

[CT]

They are created by inconsistencies in the glass.

[Clanad]

Hmmm.... Charle's Law isn't at work here, since the temperature is assumed to be constant (V/T=a constant). however Boyle's Law is at work and you've stated it, inadvertently perhaps, as it applies to gas in solution. The lower pressure is at the top of the container and the bubbles indicate the gas coming out of solution as it is forced to the area of lower pressure. Fact is, if you observed closely, bubbles are forming on the sides of the container as well... interesting question, though...

[brachiopod]

Some types of glasses (usually found in pubs) have rough etchings or an etched logo on the inside base of the glass. This is known as a 'head retention' glass. The bubbles of CO2 are encouraged to come out of solution, or exsolve, and help keep the head (froth) on the beer.

What happens is that gases in solution exsolve more easily on 'pointy' or sharp edges. Under a microscope, the etching makes the glass a 'mountain range' of jagged edges, and so this encourages the bubbles to form more than a smmoth surface would.

It is a similar principle to the 'condensation nucleii' mentioned in the thread about mist / freezing fog about eight questions below this one. In this case, they serve as 'exsolution nucleii'.

[brachiopod]

*smooth* surface !!!

"smmoths" are those butterfly-like things that come out at night !!

[einsteinsdog]

Right .........just checked this out to be sure of the facts

Poured a glass of flavoured fizzy water and another glass of plain fizzy water. In both cases the bubbles were mainly forming near or on the bottom . This is plainly a contravention of what would be expected, and as yet there dosent appear to be an explanation.............why would greater pressure cause the gas to come out of solution , its supposed to work the other way round. Clearly the laws of physics have been routed by an amateur experimenter !!

[brachiopod]

I too, checked this out, me old pup.

The first I poured into a smooth glass, and I observed a few bubbles forming.

Into the second, an etched logo glass I *ahem* acquired from a public house, I poured a second fizzy drink. In this example I saw no bubbles. Not a thing.

I then realised that my light bulb had worn out, the tungsten filament had degraded and the bulb had blown......

;o)