Coke And Ice Physics Mystery

[Dr Adequate]

I've noticed that if I put ice in a cup and then add Coke to it the ice stays at the bottom rather than floating to the top. Giving it a little push makes it rise. It's like the laws of physics need a gentle reminder to do their thing.

Can anyone explain this? Indeed, can anyone reproduce this effect? (If not, call Randi and tell him that I have powers to make ice sink.)

If it's relevant, the Coke is diet and the cup is one of those big plastic cups they sell drinks in at 7-11.

[One Skunk Todd]

if the ice is tight in the cup, I think it expands slightly as the some of the added liquid freezes among the cubes. This causes it to lock tight against the sides of the cup until you release it by squeezing the cup and changing it's shape.

[Dr Adequate]

No, it doesn't seem simply to be wedged.

I'll try it again with a single ice cube to make absolutely sure. Watch this space.

[Doctor Evil]

Perhaps a small amount of the Ice melts, and then freeze again at the bottom of the cup, making the rest of the ice stick a little. Just a guess.

[Reality Check]

It is probable that the ice is just sticking to the bottom of the cup. The bottom may not be very smooth. Thus the ice will not float untill you unstick it with a nudge.

If you tilt the cup before adding the cola does the ice shift?

[Roboramma]

Perhaps a small amount of the Ice melts, and then freeze again at the bottom of the cup, making the rest of the ice stick a little. Just a guess.

Or the bottom of the cup is slightly moist, so when you put the ice in it, it freezes to the bottom? When I touch ice fresh from the freezer with my bare hand, it sticks a little...

[Tiktaalik]

Or maybe the extreme amount of fizzy in diet sodas makes the liquid less dense until some of the fizz bubbles out, so the ice can't float at first, but then floats later...

[Doctor Evil]

Or maybe the extreme amount of fizzy in diet sodas makes the liquid less dense until some of the fizz bubbles out, so the ice can't float at first, but then floats later...

That should be easy to check.

[Pantaz]

I see this fairly often, but only when I have rinsed my glass just prior to adding the ice.

[Singularitarian]

I've noticed that if I put ice in a cup and then add Coke to it the ice stays at the bottom rather than floating to the top. Giving it a little push makes it rise. It's like the laws of physics need a gentle reminder to do their thing.

Can anyone explain this? Indeed, can anyone reproduce this effect? (If not, call Randi and tell him that I have powers to make ice sink.)

If it's relevant, the Coke is diet and the cup is one of those big plastic cups they sell drinks in at 7-11.
The coldness of the ice literally ''sticks'' to the bottom of the container, it seems. Ice is sticky remember.

[shadron]

The coldness of the ice literally ''sticks'' to the bottom of the container, it seems. Ice is sticky remember.

Hoo, boy. Coldness is an attribute of matter, a measure of the amount of heat the material contains. It cannot "stick" to anything.

If ice can be tested purely in its solid state, I would imagine it is about as sticky as the equivalent glass. Since it is rarely that cold, it's not sticky at all, particularly when presented with a pressure which melts a small interface, as in ice skating. To pieces of ice, touching under pressure melt a small amount at the interface, which will subsequently freeze, welding the ice together.

The only way in which ice might be termed sticky is if it freezes around or against some object, where the melted interface can form into microscopic cracks and crevasses on the surface of the other material and subsequently freeze. Then it becomes not just sticky but bound fast, like Portland cement.

[scratchy]

Could it be that the surface tension of the bubbles creates sort of a glue between the glass and the cubes?

[blutoski]

I did a quick experiment in a plastic cup. It did stick sometimes.

My impression is that the ice cubes are cold and large enough such that when you pour liquid over them, they freeze a little bit of the liquid quickly, cement together and sometimes also cement to imperfections on the cup's surface.

[Professor Yaffle]

OK - with that solved, why does ice melt faster in lemonade than in coke? Is it to do with the concentrations of the solutes in each?

[LibraryLady]

God, I wish my brother were alive.


And, no, that is not a nonsequitor. He was a physicist and wrote his masters thesis on properties of ice, I think. I used to call him with these types of questions all the time.

[JoeTheJuggler]

And, no, that is not a nonsequitor.
Ahem! You of all people!

Non sequitur.
;)

[blutoski]

OK - with that solved, why does ice melt faster in lemonade than in coke? Is it to do with the concentrations of the solutes in each?

Is that actually true?

My impression is that melting is just a heat transfer.If they're both basically water starting at the same temperature, then they contain the same energy per cc and I would expect no difference in melting rate.

Possibility: could the environmental temperature be an issue? Are you drinking lemonade at the beach in July, but you drink Coke in cooler weather?

[sol invictus]

Is that actually true?

My impression is that melting is just a heat transfer.If they're both basically water starting at the same temperature, then they contain the same energy per cc and I would expect no difference in melting rate.


The freezing point of water depends on salinity, and probably on the concentration of other dissolved substances. So it could be that lemonade has a lower freezing point, which presumably means the ice immersed in it would melt faster.

Another possibility is that lemonade is a better heat conductor. In many materials heat conductivity tracks electrical conductivity. Pure water is a very bad electrical conductor, but water with contaminants is much better. (There's convection, but it's hard to see how that could change much.)

Still another is acidity - maybe that helps melt the ice.

[blutoski]

The freezing point of water depends on salinity, and probably on the concentration of other dissolved substances. So it could be that lemonade has a lower freezing point, which presumably means the ice immersed in it would melt faster.

My interpretation of the question was that it was about the icecubes melting, not about the lemonade freezing.



Another possibility is that lemonade is a better heat conductor. In many materials heat conductivity tracks electrical conductivity. Pure water is a very bad electrical conductor, but water with contaminants is much better. (There's convection, but it's hard to see how that could change much.)

Still another is acidity - maybe that helps melt the ice.

I hadn't thought of this. Is lemonade really more acidic than Coke? (probably depends on the lemonade)

[sol invictus]

My interpretation of the question was that it was about the icecubes melting, not about the lemonade freezing.

Yes, but they're not unrelated, and I suspect an ice cube floating in salt water will dissolve faster than one in pure water.

For example, suppose the water is at -1 C and the salt content such that it remains liquid at that temperature. I think the ice cubes will melt, whereas they obviously wouldn't if the water had no salt in it and were frozen.

[Singularitarian]

Hoo, boy. Coldness is an attribute of matter, a measure of the amount of heat the material contains. It cannot "stick" to anything.

If ice can be tested purely in its solid state, I would imagine it is about as sticky as the equivalent glass. Since it is rarely that cold, it's not sticky at all, particularly when presented with a pressure which melts a small interface, as in ice skating. To pieces of ice, touching under pressure melt a small amount at the interface, which will subsequently freeze, welding the ice together.

The only way in which ice might be termed sticky is if it freezes around or against some object, where the melted interface can form into microscopic cracks and crevasses on the surface of the other material and subsequently freeze. Then it becomes not just sticky but bound fast, like Portland cement.


Next winter then, just lick a pole outside when its frosty and lets see if you actually still think what you think.

[Singularitarian]

I did a quick experiment in a plastic cup. It did stick sometimes.

My impression is that the ice cubes are cold and large enough such that when you pour liquid over them, they freeze a little bit of the liquid quickly, cement together and sometimes also cement to imperfections on the cup's surface.

Precisely.

[Ysidro]

Goddit. Or aliens. Or alien bigfeets.

[Dr Adequate]

Yes, careful experiments have shown that it was just freezing to the bottom --- what surprises me it how quickly it does so.

Thanks for the suggestions.

[shadron]

Next winter then, just lick a pole outside when its frosty and lets see if you actually still think what you think.

Riiiiiight. And that's what you meant?

[Singularitarian]

Riiiiiight. And that's what you meant?

Yes.

[Professor Yaffle]

Is that actually true?

My impression is that melting is just a heat transfer.If they're both basically water starting at the same temperature, then they contain the same energy per cc and I would expect no difference in melting rate.

Possibility: could the environmental temperature be an issue? Are you drinking lemonade at the beach in July, but you drink Coke in cooler weather?

My comparison is in the same environment. Its when I order a lemonade and my husband orders a coke; the drinks have the same amount of ice in them, but mine always melt away to nothing while his are still relatively large. It always pees me off because I like to crunch the ice cubes when I have finished the drink and I often don't have any left to do that while he has lots.

[Hokulele]

The coldness of the ice literally ''sticks'' to the bottom of the container, it seems. Ice is sticky remember.


Tell that to a figure skater.

[Soapy Sam]

My comparison is in the same environment. Its when I order a lemonade and my husband orders a coke; the drinks have the same amount of ice in them, but mine always melt away to nothing while his are still relatively large. It always pees me off because I like to crunch the ice cubes when I have finished the drink and I often don't have any left to do that while he has lots.

Is it possible you hold your glass more than he does?

Tell that to a figure skater.

Very different contact surface pressures. Ice on glass maybe 1g/cm^2. Ice skate blade maybe 7000g/cm^2, ball park guesstimate. It would be reasonable to expect different behaviour.

[blutoski]

My comparison is in the same environment. Its when I order a lemonade and my husband orders a coke; the drinks have the same amount of ice in them, but mine always melt away to nothing while his are still relatively large. It always pees me off because I like to crunch the ice cubes when I have finished the drink and I often don't have any left to do that while he has lots.

I wonder if the CO2 withdraws heat from the fluid when it bubbles out? (entropy pulling heat out of the fluid)

[blutoski]

Yes, but they're not unrelated, and I suspect an ice cube floating in salt water will dissolve faster than one in pure water.

For example, suppose the water is at -1 C and the salt content such that it remains liquid at that temperature. I think the ice cubes will melt, whereas they obviously wouldn't if the water had no salt in it and were frozen.

I see what you're saying. Sort of an engineering question, as the composition of the fluids is probably complex, and lemonade's composition probably varies from brand to brand.

[Ethan Thane Athen]

My comparison is in the same environment. Its when I order a lemonade and my husband orders a coke; the drinks have the same amount of ice in them, but mine always melt away to nothing while his are still relatively large. It always pees me off because I like to crunch the ice cubes when I have finished the drink and I often don't have any left to do that while he has lots.

You've probably got hotter hands (mine are always warm, my wife's always cold). Try having the coke next time whilst he has the lemonade. If yours still melts first then case closed...

[Ysidro]

According to "G.I. Joe: The Rise of Cobra", ice sinks. Therefore the question should be "why does it eventually rise to the top?" My guess is the same as before: god, aliens, alien bigfeets.

Or a Cobra ice levitation machine that makes all the ice in the lakes rise to the surface so fish can survive and ... no wait...

[ponderingturtle]

Yes, careful experiments have shown that it was just freezing to the bottom --- what surprises me it how quickly it does so.

Thanks for the suggestions.

You could prevent this by letting your ice warm up before using it.

And no this is not silly, if the ice was at the point of phase transition instead of cooled well below phase transition it would not freeze water to it when it gets hit.

So if you say take the ice out of a glass of ice water then use it with the soda this should never happen.

[ponderingturtle]

The coldness of the ice literally ''sticks'' to the bottom of the container, it seems. Ice is sticky remember.

Which is why no one ever slips and falls on it, and your main concern about black ice is suddenly sticking solid right in the middle of the road...

[Singularitarian]

what has black ice got to do with this?

And it has to do with pressure on certain surfaces which causes the 'sticky effect.' And i am not talking about conventional glue here, as some where quick to surmize.