Freezing bubble *

Why does the bubble start freezing at the top ?

Tau.Neutrino said:

Freezing bubble *

Why does the bubble start freezing at the top ?

think about it.

?? it starts at the top and bottom

Ice is less dense than water, and moreso water + surfactant.

Arts said:

?? it starts at the top and bottom

Yes, but why does it start at the top ?

Wot from the bottom up to the top ?

Heat rises, scratches head.

Tau.Neutrino said:

Arts said:

?? it starts at the top and bottom

Yes, but why does it start at the top ?

Wot from the bottom up to the top ?

Heat rises, scratches head.

Ice floats on water. It’s less dense. It rises to the top.

I should say why does it start from the bottom and the top

Tau.Neutrino said:

Freezing bubble *

Why does the bubble start freezing at the top ?

Nice video by the way. Looking closely, it does start high (from equator to 3/4 of the way up) before it starts low, by a little bit.

At a guess, because the liquid layer is thinner near the top and thicker at the bottom. Thicker layers take longer to freeze.

Follow on question. Is the freezing up high from seed crystals that have been picked up from the surface during the placement of the bubble?

As ice crystals form at a bubble’s base, the change from liquid to solid releases heat. This “latent heat,” the heat that is absorbed or released in a phase transition, is trapped in the bottom of the bubble because the orb’s skin is too thin — about a hundredth of a millimeter — for heat to easily conduct.

As a result, the remaining liquid at the bottom of the bubble is warmer, and so has lower surface tension, than liquid at the top. That mismatch sets up currents in the fluid, causing the soapy water to stream from warmer to colder regions, a process known as Marangoni flow. The flow is so strong, says coauthor and engineer Jonathan Boreyko, “it’s ripping off the ice crystals that are growing from the bottom and taking them along for the ride.” Eventually, the ice crystals grow large enough that they lock into place, and the whole bubble freezes.

https://www.sciencenews.org/article/how-freezing-soap-bubble-turns-it-snow-globe

esselte said:

As ice crystals form at a bubble’s base, the change from liquid to solid releases heat. This “latent heat,” the heat that is absorbed or released in a phase transition, is trapped in the bottom of the bubble because the orb’s skin is too thin — about a hundredth of a millimeter — for heat to easily conduct.

As a result, the remaining liquid at the bottom of the bubble is warmer, and so has lower surface tension, than liquid at the top. That mismatch sets up currents in the fluid, causing the soapy water to stream from warmer to colder regions, a process known as Marangoni flow. The flow is so strong, says coauthor and engineer Jonathan Boreyko, “it’s ripping off the ice crystals that are growing from the bottom and taking them along for the ride.” Eventually, the ice crystals grow large enough that they lock into place, and the whole bubble freezes.

https://www.sciencenews.org/article/how-freezing-soap-bubble-turns-it-snow-globe

Thanks.

esselte said:

As ice crystals form at a bubble’s base, the change from liquid to solid releases heat. This “latent heat,” the heat that is absorbed or released in a phase transition, is trapped in the bottom of the bubble because the orb’s skin is too thin — about a hundredth of a millimeter — for heat to easily conduct.

As a result, the remaining liquid at the bottom of the bubble is warmer, and so has lower surface tension, than liquid at the top. That mismatch sets up currents in the fluid, causing the soapy water to stream from warmer to colder regions, a process known as Marangoni flow. The flow is so strong, says coauthor and engineer Jonathan Boreyko, “it’s ripping off the ice crystals that are growing from the bottom and taking them along for the ride.” Eventually, the ice crystals grow large enough that they lock into place, and the whole bubble freezes.

https://www.sciencenews.org/article/how-freezing-soap-bubble-turns-it-snow-globe

I think my explanation is better. Gravity drags liquid water down from the top and sides of the bubble, making the liquid water layer thicker at the bottom so it takes longer to freeze.

Latent heat can’t explain it because in order to release latent heat at the bottom the liquid has to freeze at the bottom – and it doesn’t.

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