The Physics behind Mentos and Diet Coke

[Sedalia Dave]

So as to not hijack the memes thread. Here is an explanation of why mentos candies cause the CO2 in dissolved in liquids to be rapidly released. And why it will not work if you put the mentos in an ice cube.

 

Mentos candies have a rough surface with thousands of tiny imperfections called nucleation sites. The nucleation sites allow the CO2 dissolved into liquids like soda to reform into gas bubbles. Tiny imperfections in a glass allow bubbles of CO2 to form on the glass. Same is true for a straw inserted into the liquid. Insert a pipe cleaner into a carbonated liquid and observe how many more bubbles form.

 

For more read up on nucleation here.

 

Now for the reaction. Some carbonated sodas like Diet Coke have over a 4 to one ratio of CO2 to liquid. So for every liter of soda you have 4 liters of dissolved CO2.  When you provide a nucleation site the dissolved CO2 starts to come out of solution and form a bubble. The more nucleation sites the more bubbles. Once the bubbles grow large enough they break free and float to the surface. As they do so they cause even more CO2 to be released starting a chain reaction. The warmer the liquid is the easier it is for the dissolved CO2 to be released. Same is also true for the viscosity. The less viscous a fluid is the easier it is for the CO2 to be released. Diet sodas contain less sugar and are therefore release the dissolved CO2 easier. The other ingredants in the soda also make a big difference. While Diet Coke is often used Diet Cherry Dr. Pepper will make a bigger geyser all other things being equal. 

 

Temperature also plays a big part. The colder a fluid is the harder it is for the dissolved CO2 to be released. This is why warm soda fizzes more than cold.

 

Now for why the mentos in an ice cube doesn't work. When you put the mentos into water the nucleation site are eliminated because the candy is water soluble. No nucleation sites means no place for the CO2 bubbles to form. You can easily test this theory by taking 2 mentos candies and dipping one into water before dropping them into a soda. After it settles to the bottom drop the other into the soda as it came from the package. 

 

Note mentos are also soluble in soda. However the tiny CO2 bubbles that form on the surface prevent the liquid from dissolving all the nucleation sites by creating a barrier between the liquid in the soda and the candies surface. Once all the CO2 is gone the soda will dissolve the surface of the candy and eliminate the nucleation sites.

[Pat Riot]

Thank you Dave. I am printing this and giving it to my grandson. He and his friends were trying to figure this out recently.

[Alpo]

1 hour ago, Sedalia Dave said:

Diet sodas contain less sugar and are therefore release the dissolved CO2 easier.

This wasn't mentioned in the article I read explaining it.

 

They said that while a normal soda will work, since diet soda has aspartame instead of sugar, the resulting mess is easier to clean up.

 

Unlike sugar, NutraSweet is not sticky.

[Marshal Mo Hare, SASS #45984]

Diet soda has lower surface tension than sugared coke, allowing bubbles to form more readily.

[Sixgun Sheridan]

Stupid question #237: if I eat some Mentos then chug a can of soda am I going to blow myself up?

[sassnetguy50]

14 minutes ago, Sixgun Sheridan said:

Stupid question #237: if I eat some Mentos then chug a can of soda am I going to blow myself up?

Wouldn't the saliva and stomach acid have the same effect as water, forming a barrier?

[sassnetguy50]

Just now, sassnetguy50 said:

Wouldn't the saliva and stomach acid have the same effect as water, forming a barrier?

I have seen a dry mentos placed on a tongue and a swig of diet coke.  That guy made a mess.

[Alpo]

46 minutes ago, Sixgun Sheridan said:

Stupid question #237: if I eat some Mentos then chug a can of soda am I going to blow myself up?

No, but if you eat a bunch of dried apples and then chug a bottle of water you just might.

[Forty Rod SASS 3935]

On 4/25/2022 at 12:35 PM, Sixgun Sheridan said:

Stupid question #237: if I eat some Mentos then chug a can of soda am I going to blow myself up?

Hopefully! UH......, maybe.    

 

Could simply vacate your internal plumbing in a hurry.