How Does This Work? Why do Diet Coke Mentos and Coke Zero Mentos create such exciting geysers? Itвs mostly due to a process called nucleation, where the carbon dioxide in the soda is attracted to the Mentos (they are awfully cute). That creates so much pressure that the soda goes flying. We then built nozzles that make the opening smaller and that makes the geysers go even higher. So what is nucleation about and why do Mentos release all this pressure so spectacularly? Read onв
After a lot of debate, scientists are now saying that the primary cause of Coke Mentos geysers is a physical reaction, not a chemical reaction. Their explanation is this process called nucleation. All the carbon dioxide in the soda в all that fizz в is squeezed into the liquid and looking for a way out. Itвs drawn to any tiny bumps that it can grab onto. Those tiny bumps are called nucleation sites: places the gas can grab onto and start forming bubbles. Nucleation sites can be scratches on a glass, the ridges of your finger, or even specks of dust в anywhere that there is a high surface area in a very small volume. The surface of a Mentos is sprayed with over 40 microscopic layers of liquid sugar. That makes it not only sweet but also covered with lots and lots of nucleation sites. In other words, there are so many microscopic nooks and crannies on the surface of a Mentos that an incredible number of bubbles will form around the Mentos when you drop it into a bottle of soda.
Since the Mentos are also heavy enough to sink, they react with the soda all the way to the bottom. The escaping bubbles quickly turn into a raging foam, and the pressure builds dramatically. All that pressure has got to go somewhere, and before you know it, you\’ve got a big geyser happening! Try This at Home! This is a great thing to try yourself в if youвre careful. Hereвs how. Make sure you wear your goggles and lab coats, so that you are not only protected, you also look cool as you run away from the flying soda. What happens if you drink soda and then eat Mentos? Well, a lot of the fizz goes away as you drink. Then when bubbles are released in your stomach, your stomach can expand a bit. And your stomach also has ways of, umm, releasing excess gasв The MythBusters showed that your stomach wonвt explode, but it still wouldnвt be a lot of fun. Do not, repeat, do not be stupid and test the limits of your stomach. Don\’t even think about it. What Else Works? We\’ve tested everything from Mountain Dew Lifesavers to Moxie M M\’s. Shockingly enough, dropping just about anything into just about any kind of soda creates at least a little fizz. Even some pocket change made a bottle of root beer bubble up a bit. But the combination of Coke Zero Mentos is particularly potent! Does It Have to be Diet?
Diet Coke and Coke Zero tend to go a bit higher than regular soda, because they have a little more carbonation and the sweeteners help make the reaction a little bigger. Most importantly, Coke Zero and Diet Coke arenвt sugary and sticky. Every time we set off a big geyser display, we get soaked to the skin, so itвs nice not to get covered in sugary goo. Thanks to Tonya Coffey at Appalachian State University in North Carolina for publishing a scientific study of Coke Mentos in the American Journal of Physics. has this great summary of the explanation. You can learn more about nucleation sites in action if you coat the inside of a small glass with vegetable oil. Move the glass around to get a nice smooth coating of oil and then pour in some soda. What happens? No fizz. Why? No nucleation sites. Now sprinkle in some granulated sugar. What happens? Lots of fizz! Why? Lots of nucleation sites! The eruption is caused by a physical reaction, rather than any chemical reaction. The addition of the Mentos leads to the rapid of gas bubbles The conversion of dissolved carbon dioxide to gaseous carbon dioxide forms rapidly expanding gas bubbles in the soda, which pushes the beverage contents out of the container. Gasses, in general, are more in liquids at elevated pressures. Carbonated sodas contain elevated levels of carbon dioxide under pressure. The solution becomes with carbon dioxide when the bottle is opened, and the pressure is released.
Under these conditions, carbon dioxide begins to precipitate from solution, forming gas bubbles. Normally, this process is relatively slow, because the for this process is high. The activation energy for a process like bubble nucleation depends on where the bubble forms. It is highest for bubbles that form in the liquid itself (homogeneous nucleation), and lower if the bubble forms on some other surface ( ). When the pressure is released from a soda bottle, the bubbles tend to form on the sides of the bottle. But because they are smooth and clean, the activation energy is still relatively high, and the process is slow. The addition of other nucleation sites provides an alternative pathway for the reaction to occur with lower activation energy, much like a catalyst. For instance dropping grains of salt or sand into the solution lowers the activation energy, and increases the rate of carbon dioxide precipitation. The physical characteristics of Mentos (surface roughness, easy into the liquid, etc. ) have the effect of drastically reducing the activation energy for carbon dioxide bubble formation, so that the nucleation rate becomes exceedingly high. The activation energy for the release of carbon dioxide from Diet Coke by addition of Mentos has been found to be 25 kJ mol. This formation of gaseous carbon dioxide within the water, which due to and its high wants to maintain a connected matrix of molecules, causes the water to, ultimately generating the \”jet\”or \”geyser\”or eruption-like nature of the effusion.
The foaming is aided by the presence of food additives such as, sugars, and flavorings in Diet Coke, and and in the Mentos candy, all which influence the degree to which water can foam. The nucleation reaction can start with any heterogeneous surface, such as rock salt, but Mentos have been found to work better than most. Tonya Coffey, a physicist at, found that the in lowers the in the water and causes a bigger reaction, but that does not accelerate the process. It has also been shown that a wide variety of beverage additives such as sugars, citric acid, and natural flavors can also enhance fountain heights. In some cases, dissolved solids that increase the surface tension of water (such as sugars) also increase fountain heights. These results suggest that additives serve to enhance geyser heights not by decreasing surface tension, but rather by decreasing bubble coalescence. Decreased bubble coalescence leads to smaller bubble sizes and greater foaming ability in water. Thus, the geyser reaction will still work even using sugared drinks, but diet is commonly used both for the sake of a larger geyser as well as to avoid having to clean up a sugary soda mess.