Heterogeneous nucleation - Mentos and coke

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In summary, the conversation revolved around the Mentos and diet cola experiment and the phenomenon of Heterogeneous Nucleation. The main questions were about why the CO2 in the coke turns into gas instead of solid, why this mainly happens when the Mentos sinks to the bottom, and whether the liquid and CO2 are still pressurized after the eruption. It was also mentioned that while the process of nucleation was somewhat understood, there was still some confusion about it. The response stated that the CO2 remains a gas because it starts off that way and that the cola and CO2 form a supersaturated solution. It was also mentioned that there is a loss of pressure due to the nucleation process. The conversation also included a
  • #1
Kruler
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Hello guys , I'm a medical student , and I'm very fascinated by this Mentos and diet cola experiment , however i do not understand it completely and i would like to know the followings
-From my understanding it happens because of Heterogeneous Nucleation , is that right ? Then i do not undertand why is the CO2, which starts as liquid form turns actually into gas ? isn't supposed to turn into solid by common logic ? I don't really understand that.
-Why is that happens mainly when the mentos sinks at the bottom of the coke ?
-After this phenomenon, is the liquid (coke) + CO2 still pressurized ? if its not , why is it losing it's pressure ?
-Last question about the pressure - does a super-pressurized coke will produce an higher eruption ?

I read some in the internet , but every website explains the Nucleation process differently , i think i understand it , but not fully though.

I asked a lot of questions , but I'm really curious :)
 
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  • #2
Then i do not undertand why is the CO2, which starts as liquid form turns actually into gas ? isn't supposed to turn into solid by common logic ?

The C02 starts off as a gas disolved in the coke. It stays a gas.
 
  • #3
CWatters said:
The C02 starts off as a gas disolved in the coke. It stays a gas.
Thanks for the reply , so i assume that the cola + CO2 is a supersaturated solution , why is the mentos and the nucleation causing it to lose pressure ?
 
  • #4
sry for bumping guys , i would really appreciate if anyone knows a good webpage / article / book about nucleation (except wiki)
 
  • #5


Hello there! I am happy to provide some answers to your questions about heterogeneous nucleation and the Mentos and coke experiment.

Firstly, you are correct in your understanding that the Mentos and coke experiment is a result of heterogeneous nucleation. This is a process where gas molecules (in this case, carbon dioxide) are able to form bubbles more easily on a surface (the rough surface of the Mentos candy) than in the surrounding liquid. This leads to a rapid release of gas, resulting in the fizzy eruption we see in the experiment.

Now, to address your question about why the CO2 turns into gas instead of solid. When the Mentos candy is dropped into the coke, it causes a sudden increase in the surface area of the liquid. This leads to a decrease in pressure, which causes the dissolved carbon dioxide gas to come out of solution and form bubbles. The gas molecules then expand and rise to the surface, creating the foamy eruption we see.

As for why this happens mainly when the Mentos sinks to the bottom of the coke, it is because the bottom of the bottle has a higher concentration of dissolved carbon dioxide due to the pressure from the gas in the bottle. This means that there are more gas molecules available to form bubbles when the Mentos is dropped in.

After the eruption, the liquid (coke) and CO2 are still pressurized. However, some of the gas has been released in the eruption, leading to a decrease in pressure. This is why the bottle may not feel as hard or pressurized after the experiment.

Lastly, regarding your question about whether a super-pressurized coke will produce a higher eruption, the answer is yes. The more dissolved carbon dioxide in the liquid, the more gas molecules available to form bubbles and create a larger eruption.

I hope this helps to answer your questions and increase your understanding of heterogeneous nucleation and the Mentos and coke experiment. Keep asking questions and exploring the world around you!
 

Related to Heterogeneous nucleation - Mentos and coke

What is heterogeneous nucleation?

Heterogeneous nucleation is the process in which a solid substance (such as a Mentos candy) acts as a catalyst for the formation of bubbles in a liquid (such as coke).

Why do Mentos and coke create such a dramatic reaction?

The surface of a Mentos candy is covered in tiny pits and bumps, providing a large surface area for the carbon dioxide gas in the coke to quickly form bubbles. This reaction is also accelerated by the presence of nucleation sites on the candy's surface, such as microscopic cracks or imperfections.

Is this reaction specific to Mentos and coke or can it occur with other combinations?

While Mentos and coke are a popular combination for this experiment, similar reactions can occur with other combinations of nucleation sites and carbonated liquids. For example, adding sugar or salt to a carbonated drink can also cause a rapid release of bubbles.

Is the reaction affected by the temperature of the liquid?

Yes, the reaction is more dramatic when the coke is warm rather than cold. This is because warm liquids have a lower surface tension, making it easier for bubbles to form and rise to the surface.

Can this reaction be dangerous?

While the reaction may seem explosive, it is not dangerous as long as it is done safely and with caution. It is important to follow proper safety precautions, such as wearing safety goggles and conducting the experiment in a well-ventilated area, to avoid any potential hazards.

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