Notes & Queries:

I was explaining to my Nat 5 physics prelim sitting son that an example of latent heat capacity is the fact that if I leave a room temp bottle of Heineken in the freezer for 35 mins it will cool down to a nice chilled temperature. I then have a 20 minute leeway while it remains exactly the same chilled temp before it actually freezes. This 20 mins is the period in which its latent heat of fusion gets stripped out of it.

Then tonight, I’d forgotten about the beer and fished it out the freezer a bit late. It was still liquid though so I thought I’d saved it. But then when I opened it and it was exposed to the warm air it started rapidly freezing from the surface down. What happened?

mmm… could be a pressure thing. As it approaches freezing, it expands (ice being bigger than water), but has no room to do so, so freezing is actually delayed slightly.

The rapid decompression from opening the bottle, though, catalyses the freezing process?

(Or something, I’m not a physicist!)

https://www.thenakedscientists.com/get-naked/experiments/freezing-lemonade-bottles

Co2 volatising

Possibly the bubbles provided nucleation sites for ice crystals to form.

Did you drink it?

Thanks all, that naked scientist site has explains it all very patiently!

I was going to say nucleation of the super cooled liquid on the bubbles.

Did you drink it?

Of course I drink it, it’s a lager slush puppy. It’s not very nice though.

Damit, yes nucleation. Creating a new surface takes a lot of energy due to the surface tension. So you need somewhere for it to start and the bubbles provide that.

You can achieve the same thing (very dangerously) heating water in the mocrowave. Because the water is heated more evenly and not against a hot surface (which provides both the surface and the energy) you can bring it up over 100C without boiling. You then get a facefull of boiling water when you stir it with a spoon and introduce air/bubbles.

It’s Heineken – doesn’t matter what you do to it it still won’t be nice 😀

This has tickled my science bones a lot. I am going to (maybe) try the lemonade thing tomorrow and then figure out where I can crowbar it into a lesson.

If you use a very smooth very clean glass. ( Try with lemonade if it bubbles from one spot it’s not smooth enough.) You can supercool water. Then drop a salt crystal in it freezes from that point. It’s pretty amazing.

In a lab a beaker and deionised water work best.

During the ‘Beast From the East’ I was working in my unheated workshop – and had some cans of San Peligrino and bottles of water which were freezing like this when I opened them. Which was fascinating but not much help In solving the thirst problem.

I don’t think it’s nucleation on the bubbles as the glass will provide ample sites for freezing to begin. I’d have thought it was pressure depressing the freezing point of the liquid.

I feel an experiment coming on…

I’d have thought it was pressure depressing the freezing point of the liquid

In the link above it explains that it’s dissolved CO2 depressing the freezing point, but I think the pressure would do so as well.

Pressure doesnt affect the melting point fo that extent untill you get into much higher pressures, e.g. your bodyweight on an ice skates edge.

I then have a 20 minute leeway while it remains exactly the same chilled temp before it actually freezes. This 20 mins is the period in which its latent heat of fusion gets stripped out of it.

I don’t understand this phenomenon. The latent heat is only removed when some beer freezes. So the sequence should be: liquid and getting colder; constant temperature solidifying; solid and getting colder. So I don’t know why your beer is staying at a constant temperature but not freezing.

Irrelevant but amusing

Freezing booze is one method of removing most of the water to get a liqueur. Beer liqueur is disgusting, like over-strong barley wine.

SL2000 – You’re right, if it isn’t solidifying then there’s no phase change and thus latent heat of fusion doesn’t really apply, just normal specific heat capacity as it super cools.

if it isn’t solidifying then there’s no phase change and thus latent heat of fusion doesn’t really apply

ok I got that wrong then. I thought that in the undernoted graph the horizontal bits meant that the beer stayed in its original state until sufficient energy had been added/subtracted that it got to the end of the temperature plateau (in whichever direction it was going) and at that point it would change state.

http://www.alevelphysicsnotes.com/thermal_physics/latent_heat.phphttp://www.alevelphysicsnotes.com/thermal_physics/latent_heat.phphttp://www.alevelphysicsnotes.com/thermal_physics/latent_heat.php

Not quite, it’ll stay about the same temp as the phase changes gradually until all the liquid is solid (I.e. the latent heat bit is finished) and then the solid (ice) starts to cool down until gets to -20 or whatever your freezer is at. Because in the example above the phase change (solidification) doesn’t happen (which is where the latent heat comes in) the liquid just keeps on cooling down. When the bubbles happen the ice forms very quickly as there’s a bunch of ‘extra coldness‘ kicking around (I.e. in the super cooled liquid). The beer should actually warm up as the ice forms once it’s opened and nucleation happens, as the liquid releases heat as it solidifies. In the graphs it’s the phase change that releases heat, so the temperature stops dropping until solidification is complete. Of course this is beer, not pure water, so things will be thrown off a wee bit by that, but the principles should be the same.