rashbre central: coke and mentos

Friday, 16 June 2006

coke and mentos

cokeandmentos.jpgMost people have seen the Diet Coke and Mentos videos where you add Mentos to a Coke bottle and watch the science. The most basic is to just drop a few Mentos into the top of a 2 litre Coke bottle (Two litre because of the wider screw neck) which creates a rather spectacular fountain.

Coke and other fizzy drinks have a lot of compressed Carbon Dioxide in them. The Mentos, with their gnarly rough surface comprise thousands of tiny pits which are perfect places for carbon dioxide bubbles to form as it wants to desperately escape from the prison of the coke liquid. This 'nucleation' is like when the rough spots in a beer glass allow bubbles to form that that rise to the top of the beer. The other Mentos component is the gum arabic used as a binding agent. This reduces the surface tension in the Coke, making it more slippery.

So when the Mentos hit the Coke, the Carbon Dioxide bubbles form really fast in all of the tiny pits. This gas pushes the slippery liquid out of the bottle at jet propelled speed. So a fountain or a more advanced rocket become easy projects, (with safety goggles and outdoors). Trying this in, say, a kitchen would be devastating. In the mouth this can create concussion. Seriously.

So lets see a few experts such as the well known eepybird video using 200 litres of Coke and 500 Mentos which attempts to simulate a Las Vegas Bellagio Hotel fountain moment, but I prefer the more extreme rocket versions.

Now Italian-owned Mentos spends less than $20m per annum on US advertising. The blogosphere word of mouth advertising of this is reckoned to be worth more than $10m with over 800 Coke 'n Mentos videos (many from cellphones) on the web and counting...

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