Melting Ice in Beverages

Would ice melt faster in Water, fruit punch or Cola?
- K.Cooke
Tampa,Fl-USA

[The following answer was posted originally, and is left in in order to make sense of the follow-ups. It is not correct, however. Among the  things that it leaves out is that any solute lowers the melting point of water, which speeds melting if other things are equal. Among the things it gets wrong is the implication that cola is less dense than water.] Ice will melt fastest in whichever drink will move around the ice cube the most. If you drop an ice cube in a glass of warm liquid, then as the ice melts, the cold liquid from the ice cube moves to the bottom of the glass while warmer liquid moves up to take its place (this is because warm liquid is less dense than cold liquid and it floats). The faster this happens, the more warm liquid will be up against the ice cube, and the faster it will melt.

I would suspect that the Cola would melt the ice the fastest because it is carbonated. Carbonation makes the density of the Cola even lower than it would be otherwise, so the Cola will float up to the top very quickly as the ice melts. But the only way to be absolutely certain of this is to try it yourself.

-Tamara

(published on 10/22/2007)

I tried the experiment and found that ice melted faster in the water at room temperature than a carbonated drink. Why did that happen?
- Lexady (age 12)
Pleasant Grove, Utah, USA

Actually, contrary to the previous answer, carbonated drinks are usually denser than water. That means that the water from the melted ice may tend to float on the surface, insulating the ice cube from the warmer liquid. The main reason for the increased density of the drink is the dissolved sugar. I'm not positive whether the carbonation increases or decreases the density.*

Mike W.

Lee H

*[note added years later] Dissolved CO₂ increases the density of H₂O. The CO₂ has about 2.5 times the molecular weight and takes up more or less the same amount of volume per molecule. Why we didn't say that before is a mystery. Of course, once the pressure is released on the carbonated water, tiny bubbles start to form, and they decrease the density, so maybe the effect is complicated. /mbw

(published on 10/22/2007)

i tried an experiment with various liquids and the pop is the slowest melting liquid but i think it might just be that the pop is warmer than the other liquids, even though i put them all in the fridge for an hour? Do you think its just the temperature?
- Chad
Iowa, USA

If you leave these liquids in the fridge for long enough, they'll all reach the same temperature. That's a result of a basic law of thermodynamics.
It's possible that an hour wasn't quite long enough. It's easy to check- just leave them in overnight next time.

If the pop is still the slowest, you can check other factors. Were all the liquids in similar sizes and shapes of containers? Were they sitting in the same environment as they melted, equally exposed to warm air or water?

If the effect persists, then there are other explanations to check. One that we've discussed before is that ice melting on salt water or sugar water tends to sit in a pool of very cold recently melted water on top. In water that that doesn't have solutes making it denser, the melted ice mixes more with the rest of the water, speeding the flow of heat to the ice.

Mike W.
Leh

(published on 10/22/2007)

I melted ice cubes in 5 different liquids: diet coke, orange juice, lemonade, milk and V-8 vegetable juice. All juices were at room temperature, in identical amounts, and identical amounts/size of ice cubes. Diet Coke melted the ice cube fastest, but the V-8 took nearly three times the amount of time to melt the same size cube. I think it was because V-8 is thicker? Am I correct?
- Peter (age 10)
Norwalk, CT

Peter- we aren't sure, but that sounds like a very good guess. V-8 is "thick" in two ways. It is dense, meaning that a cup of it weighs quite a bit more than a cup of pure water. That has the effect we wrote about above, of making the cold melted water from the ice just sit on top, around the ice cube. The V-8 also flows less easily than pure water, because it's kind of sticky. (The fancy word for that is "viscous".) That probably also helps keep the cold water and the V-8 from mixing.

Here's a possible experiment you could try.
Filter the V-8 through a coffee filter, and then try it. What comes through the filter should be chemically almost like the liquid in the V-8, but missing the pieces of stuff that make it extra dense and more viscous. I bet it then acts more like orange juice.

Mike W.

(published on 01/23/2011)

Does baking soda make ice melt faster than pepper?
- heather (age 13)
CA lemon cove

Certainly the baking soda will lower the melting point of the ice more than the pepper. The amount the melting point lowers depends on how many particles get dissolved in each drop of the melted ice. Baking soda breaks up into molecules and ions, so a little bit of it makes lots of particles. For the most part ground pepper stay as little chunks, each with huge numbers of molecules, so it makes hardly any dissolved particles per drop.

I suppose the pepper could have a few loose molecules on the surface that could help melt the first tiny bit of the ice, but by the time you've melted enough to see easily, the baking soda will be doing a much better job.

Mike W.

(published on 04/13/2011)