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What Happens when You Mix Salt and Coke?

Last updated on August 18th, 2021

what happens when you mix salt with coke

If you’ve ever wondered what really happens when salt and Coke get mixed together, you’re in luck.

We are here to finally resolve that mystery.

So what happens when you mix salt and Coke together?

It explodes. The mix fizzes a lot and foams out of the bottle, overflowing like a geyser.

The foam fountain that shoots out may reach a peak height of 6 to 8 in. So the YouTube videos with foam shooting 2 or 5 feet into the air are an exaggeration.

  • So why does this happen?
  • What is the secret behind all of that amazing fizz and foam?

Let’s get into the science behind this incredible phenomenon and explore it in depth.

Why Soda & Salt Forms a Geyser Happens

The reason why the salt mixed with the Coke creates such a foamy, explosive mess is that it undergoes a reaction known as nucleation.

Because the drink is carbonated, it contains carbon dioxide gas to make it fizzy and bubbly.

Most of the carbon dioxide gas in the soda is in solution.
That is, the carbon dioxide gas is dissolved in the liquid soda, and the soda bottle is pressurized to keep the carbon dioxide gas dissolved in solution.

However, some of the carbon dioxide comes out of solution and goes into the air above the liquid.

This is why you can observe bubbles forming in the Coke and rising to the surface of the soda, and this is also why bottles of soda which have not yet been opened are hard, because the gas within the bottle creates a high pressure environment.

When you open a bottle of soda and pour some into a glass, you can see many bubbles forming in the soda that bubble up to the surface of your drink.

The glass gives the carbon dioxide gas a surface from which bubbles can form.

When salt is poured into the soda, each grain of salt provides a series of rough surfaces on which carbon dioxide can come out of solution and form into numerous bubbles.

Each grain or crystal of salt is rough and has a lot of surface area on which multiple carbon dioxide bubbles can form.

As more bubbles form and cling to the surfaces of the salt crystal, the carbon dioxide gas bubbles become more and more buoyant.

That effect is multiplied by the number of grains which are poured into the soda (which is a lot of crystals of salt), resulting in an enormous number of tiny carbon dioxide gas bubbles gaining more and more buoyancy, thus increasing in pressure and seeking to rise to the surface.

As the carbon dioxide bubbles rise to the surface, they push all the soda in the way to rise up as well, creating a foamy geyser effect that shoots up out of the bottle and overflows to the surrounding area.

Nucleation is defined simply as the process in which matter starts to change from one phase or state to another phase or state.

Thus, the nucleation that takes place during the reaction of the salt with the Coke is the rapid changing of dissolved carbon dioxide gas (in solution) into all the carbon dioxide gas bubbles that form on or around the surfaces of the thousands of crystals of salt that are poured into the Coke.

What Do You Mix with Coke to Make It Explode?

So, besides salt, what else can you mix with Coke in order to make it explode? Putting Mentos candy into a bottle of Coke produces a similarly impressive reaction.

Reasons Why Mentos Candy Causes the Reaction: 

  • A Mentos candy has a rough surface and possesses a fairly high ratio of surface area to volume, thus providing the carbon dioxide gas with ample surface area to form numerous bubbles, which in turn create even more bubbles.
  • Mentos candy is relatively dense and will drop to the bottom of the bottle quite fast, allowing for the speedy formation of bubbles. Mentos candy that has been crushed sinks more slowly to the bottom of the Coke bottle and creates a much less explosive foam fountain that is significantly shorter in height.
  • The surface tension of the liquid affects how fast bubbles will form. Lower surface tension will allow bubbles to form more quickly. Research has shown that gum arabic, a surfactant which is contained in the coatings of Mentos candy, serves to reduce surface tension in liquid, which results in taller fountains from Mentos candy (as opposed to other mints with rough surfaces which were tested that lack gum Arabic).

Note: Using Diet Coke in this reaction also creates a much taller, more explosive geyser than using regular Coke, because the aspartame used in Diet Coke gives the liquid lower surface tension than the sugar used in regular Coke.

Diet Coke produces a much larger explosion overall, whether you use Mentos candy or salt for the reaction. Foam geysers as high as 10 meters have been reported with the use of Diet Coke.

Can Coke and Salt Stop Diarrhea?

You may have heard that drinking soda with salt is a good way to replenish your fluids if you are suffering from diarrhea.

It is true that drinking flat soda or flat soda with some salt added to it will prevent you from becoming dehydrated by replacing your fluid and electrolyte balance.

However, it matters what kind of soda you drink.

Coke contains caffeine, which research has shown may actually worsen your diarrhea symptoms.

Thus, it is not generally advisable to try to drink Coke or Coke with some salt added in order to cure your diarrhea or stop you from being dehydrated. You run the risk of worsening your condition.

In order to keep yourself from being dehydrated, try to drink flat Sprite or flat 7UP instead, which does not contain caffeine.

You can add a bit of salt to one of these types of soda in order to aid in restoring your electrolyte balance.

Why Do People Put Salt in Soda?

People may put salt in soda in order to watch it explode and foam up, as was described earlier.

However, let us assume that these people are not looking for this particular nucleation reaction which results in a geyser of soda.

The simple answer as to why people put salt into soda is that it makes the soda flat very quickly.

The nucleation reaction which was described earlier quickly gets rid of most of the carbon dioxide in the soda (by releasing it in the form of many bubbles which foam up and create a geyser).

Putting some salt into soda gets rid of the carbonation and allows it to be drunk flat, which may be necessary for some who have an upset stomach.

Also, salt in the soda will aid in restoring proper electrolyte balance for those who are suffering from diarrhea.