Jason EganWhat's the story with Mentos explosions in Diet Coke bottles?
September 9th 2006 03:53
A great method to showcase your claim to juvenile delinquency: Add some ‘Mentos’ (mint candies) to ‘Diet Coke’ (soft drink). Here is a quick illustration by some people more than willing to demonstrate (definitely no shortage there):
How cool is that.
OK you are either saying: “Wow!” or “Yea yeah I have seen/heard that one before…” or just plain “Idiots.” But what is happening inside the bottle?
As you can probably imagine from the crazy explosion, there is some chemistry involved. Diet Coke, or any soft drink, is basically sugar (or artificial sweetener), flavouring, water and preservatives.
Now soft drinks contain carbon dioxide gas (making it bubbly). Until a bottle is cracked open, the gas cannot form any bubbles, and remains suspended in the liquid. This drives the gas bananas, because all it wants to do is form bubbles!
When a soft drink bottle is shaken and opened, the carbon dioxide gas is released from the water, escaping violently from the bottle (along with the liquid).
But are there other ways to let this gas escape? If you drop anything into some soft drink, just watch how quickly bubbles form on the surface. If you put salt in there, it foams up like anything, as lots and lots of bubbles form on each salt crystal.
Now back to the bottle of soft drink. There are many water molecules inside this container. They all attract strongly to each other, and join to form a net around each individual carbon dioxide molecule – holding it down. To form a bubble, or even expand an already existing bubble in the liquid, the water molecules will need to push away from each other. This takes extra energy and – you guessed it – the water molecules do not like it one bit. They resist ANY formation of bubbles.
When the Mentos is dropped into the soft drink, the gelatin and gum arabic in the dissolving candy easily breaks the surface tension. As a result, the net of water molecules is disturbed.
You can feel the carbon dioxide molecules licking their lips at this stage...
Now the Mentos candy has thousands of microscopic pits all over its surface. These pits are called nucleation sites, and are a great place to form the carbon dioxide bubbles. When Mentos is dropped into the soft drink, thousands of carbon dioxide bubbles are formed on the surfaces. Add to this the heaviness of the candies (they all sink to the bottom) and you have bubble overload!
As soon as the gas is released, it pushes all the liquid out of the bottle in one go, and KABOOOOM!!
There is a specific need to use the ‘mint’ variety of Mentos. The ‘non-mint’ variety does not work as well. Jamie Hyneman – from ‘Mythbusters’ (a science television show that investigated the phenomenon) – explains: “The ‘non-mint’ variety has a glaze on them, and they don’t work at all. It only works with the mint ones, because they have a matte finish. That surface serves as a little portal for the gas to escape through.”
Also, there is a specific need to use ‘diet’ soft drinks for this experiment. Regular soft drinks contain sugar, and those molecules are very large. Due to the stickiness of the sugar, they hold onto the carbon dioxide molecules better – even when the Mentos is added. All you get is a disappointing fizzle dizzle. The other point in favour for ‘diet’ drinks: It leaves a less sticky mess (due to the artificial sweetener). This may be important when you are planning large pyrotechnics!
If you are fresh out of Mentos – no problemo! Plain table salt is much better anyway, so use that on the diet soft drink.
The largest reported ‘Mentos Fountain’ is almost 5.5 metres. If you can better it, let me know...
How cool is that.
OK you are either saying: “Wow!” or “Yea yeah I have seen/heard that one before…” or just plain “Idiots.” But what is happening inside the bottle?
As you can probably imagine from the crazy explosion, there is some chemistry involved. Diet Coke, or any soft drink, is basically sugar (or artificial sweetener), flavouring, water and preservatives.
Now soft drinks contain carbon dioxide gas (making it bubbly). Until a bottle is cracked open, the gas cannot form any bubbles, and remains suspended in the liquid. This drives the gas bananas, because all it wants to do is form bubbles!
When a soft drink bottle is shaken and opened, the carbon dioxide gas is released from the water, escaping violently from the bottle (along with the liquid).
But are there other ways to let this gas escape? If you drop anything into some soft drink, just watch how quickly bubbles form on the surface. If you put salt in there, it foams up like anything, as lots and lots of bubbles form on each salt crystal.
Now back to the bottle of soft drink. There are many water molecules inside this container. They all attract strongly to each other, and join to form a net around each individual carbon dioxide molecule – holding it down. To form a bubble, or even expand an already existing bubble in the liquid, the water molecules will need to push away from each other. This takes extra energy and – you guessed it – the water molecules do not like it one bit. They resist ANY formation of bubbles.
When the Mentos is dropped into the soft drink, the gelatin and gum arabic in the dissolving candy easily breaks the surface tension. As a result, the net of water molecules is disturbed.
You can feel the carbon dioxide molecules licking their lips at this stage...
Now the Mentos candy has thousands of microscopic pits all over its surface. These pits are called nucleation sites, and are a great place to form the carbon dioxide bubbles. When Mentos is dropped into the soft drink, thousands of carbon dioxide bubbles are formed on the surfaces. Add to this the heaviness of the candies (they all sink to the bottom) and you have bubble overload!
As soon as the gas is released, it pushes all the liquid out of the bottle in one go, and KABOOOOM!!
There is a specific need to use the ‘mint’ variety of Mentos. The ‘non-mint’ variety does not work as well. Jamie Hyneman – from ‘Mythbusters’ (a science television show that investigated the phenomenon) – explains: “The ‘non-mint’ variety has a glaze on them, and they don’t work at all. It only works with the mint ones, because they have a matte finish. That surface serves as a little portal for the gas to escape through.”
Also, there is a specific need to use ‘diet’ soft drinks for this experiment. Regular soft drinks contain sugar, and those molecules are very large. Due to the stickiness of the sugar, they hold onto the carbon dioxide molecules better – even when the Mentos is added. All you get is a disappointing fizzle dizzle. The other point in favour for ‘diet’ drinks: It leaves a less sticky mess (due to the artificial sweetener). This may be important when you are planning large pyrotechnics!
If you are fresh out of Mentos – no problemo! Plain table salt is much better anyway, so use that on the diet soft drink.
The largest reported ‘Mentos Fountain’ is almost 5.5 metres. If you can better it, let me know...
Not very subtle!
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