Wrong science discipline.
This isn't chemistry, it's fizz-ics.
Did you know that the popular Diet Coke and Mentos soda geyser experiment works better at higher altitudes? Or that the average size of the bubbles formed on the scotch mints is about 6μm? Now you do, thanks to the wonders of science and those with a bubbling passion for it. A chemistry professor and a high school teacher …
But nobody seems to be investigating the real science issue here: pronunciation. Personally, I insist that it's men-toes, but the marketing fools seem to think it's men-toss. As far as I can see, it's simple: Rolos, Polos, Mentos. The allegedly "correct" pronunciation sounds like a porn genre to me.
It's probably to do with the fact that you can dissolve more of a given gas in cold water than in warmer water (whereas it's the other way round for solids: the warmer the water the more salt or whatever you can dissolve in it).
the curve for dissolved gas in water isn't linear. The maximum point is around 2 deg C, with a minimum of around 60C (as I recall), but then it increases again after that, assuming you apply enough pressure to the water to stay liquid, so that very hot water under pressure can hold onto even more dissolved gas than 34 degree water at 1 atmosphere pressure. Or something like that. And according to a few online references, several types of gasses have different curves and minimum points. In general, however, it follows the pattern I described. But none of the online references bothered to extend the curve past the boiling point at sea level atmospheric pressure, because they're not concerned about managing the water chemistry of a pressurized water nuclear reactor...
I built a screw on adapter out of a bottle cap, with a drilled out centre and attached a vertical plastic tube witha a small transverse hole for a metal pin. Screw on adapter, insert pin, load tube with Mentos. Stand clear, pull cord to remove pin.
The resulting geyser was captured on video for the wife's middle school science class.
It worked so well, some kid stole it when she demoed it at school!
if I could do an instantaneous release I could build a soda bottle rocket with the mentos-diet-coke reaction.
The idea would be to cap the bottle with the mentos [and release mechanism] inside, using a 'rocket engine' cap [of my own design], and use some kind of pull-string arrangement (through the nozzle). Then you pull the string to launch it. I've already got a nice nozzle design, complete with fin/legs to spin it, as OpenSCAD files that can be 3D printed, if anyone wants to look on github for them. Maybe it could help El Reg launch another space plane?
Cool that they got to see new places, but aren't there lots of variables that were ignored? Moisture content of the mentos in different altitudes and temperatures. Did they buy all of the soda and mentos at the same time, same batches? And as mentioned above, why that specific temperature at different altitudes?
I know enough about scientific process to ask dumb questions...
Why specifically "Diet" coke?
Is there something about Sugar (or HFCS, or Manitol, or...) that changes the behavior?
As David 132 remarked, this is more a physics thing than a chemical reaction, so I'd expect, e.g. Seltzer to work as well. So why a particular witch's brew of artificial sweeteners?
Yes, I can understand the benefit to society at large from one less bottle of that vile brew finding its way into a human digestive system.
My 12 year old grand-daughter recently investigated this as her science project.
Evidently the type of sweetener used in Diet Coke is Aspartame.
So she dissolved increasing amounts of a standard aspartame based sweetener into bottles of lemonade.
Then dropped a standard sized Mento into the mixture and measured the height of the resulting foam plume.
Her conclusion: The greater the concentration of aspartame in the solution, the higher the resulting plume.
It maybe that the nucleation is a physics effect, but the actual constituents of the solution can either increase or decrease the speed of the reaction
Why specifically "Diet" coke?
Based on informal comparisons of side-by-side pouring regular and diet sodas into glasses with ice cubes, I'm convinced that diet soda foams quite a bit more than regular.
I don't know why. Perhaps the high levels of dissolved sugar in regular soda increases surface tension and therefore decreases bubble size? Or perhaps the solubility of CO₂ as a function of temperature differs?
From my grand-daughter
As far as she understands ---Her caveat, not mine!
Artificial sweeteners such as Aspartame, act in lowering the suface tension of the liquid they are dissolved in, so producing larger bubbles and more rapidly. So more foam is produced by diet versions of both coke and lemonade as they use artificial sweeteners rather than natural sugar.
She says the foam is mainly Co2 bubbles surrounded by a thin layer of the liquid, held around the bubble of gas by the liquids own surface tension.
She also points out that increases in temperature of the drink will also reduce the surface tension.
To quote her... " The warmer the pop the more the molecules in the liquid bop around, so reducing the attraction between the molecules"
I hope this helps
"I'm convinced that diet soda foams quite a bit more than regular."
Carefully open a can of (unshaken) diet coke
Carefully open a can of (unshaken) ordinary coke
Now pick each one up in turn and slam the bottom down _hard_ on a tabletop (keep it upright, you're not trying to spill or crush anything)
Compare the resulting mess
By the way, airline cabin staff passionately HATE people who ask for diet coke at 30,000 feet because the stuff is more likely to make a mess and takes longer to pour/settle
Diet Pepsi can be just as bad. I've had a 2 litre bottle jet away across a carpark after being dropped. The shock and gas release was enough to blow the cap off and it went about 50 metres
The victim of his own (suggest suitable word here)
A colleague of mine once tried dissolving solpadine in diet coke.
This resulted in much swearing, soaked laptops and three of us announcing we were going for lunch and would, maybe, be back later depending on how long it took him to clean up.
Effervescent tablets plus coke = wooshh
A lot of the 'intermountain West' is elevated so its actually a lot easier to just go visit someone in Albuqueqeu (5000') than find a pressure chamber, especially as you're going to find supermarkets that sell both Diet Coke and Mentos.
One quirk of living in the US is that if you buy a box of sponge mix or something like that you'll find 'high altitude' instructions for cooking it along with the normal instuctions. High altitude means anything over 5000' and you really need to adjust those receipies. Even brewing a pot of tea is subtly different -- a decent cuppa needs proper 100C boiling water.
I suppose someone had to introduce a bit of greeen propaganda. You really should not add assumptions as data into science, as in the latter part of the comment.
"Therefore, discussing the results of my Coke and Mentos experiments provides a great platform to introduce students to various impacts such as ocean acidification associated with increased CO2 in the atmosphere from burning fossil fuels.” ®
cheap diet cola also works at least as well as name brand diet cola
My preference for using diet coke for this has more to do with the fact that I want to preserve the good stuff, with proper sugar. Not a fan of aspartame and yes, I understand the irony of still wanting to drink coke in that context :).
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