Friday 19 July 2013

Diet coke and mentos mint experiment

This is a very famous well loved experiment that I'm sure a lot of you science lovers out there have tried.  We done ours yesterday with the girls Nan and Grandad and Daddy and this is how it went...

This is our bottle from earlier in the week but the one in the video is a diet coke, I promise.
So how did we do it and why does it work?  Read on to find out...

Before you begin I must warn you this is an OUTDOORS ONLY experiment!  It is best done on grass as otherwise there will be a lot of tidying up left behind. 

Right, now for the fun! To perform this fun experiment you will need a 2 litre bottle of coke and a Mentos mint.  Actually any carbonated drink will do but over the time it has been found that diet coke works the best) we tried this earlier on in the week with a non-diet coke but the effect wasn't as high.
The numerous small pores on the sweet's surface catalyse (cause an action or process to begin) the release of carbon dioxide (CO2) gas from the fizzy drink, this causes the rapid explosion, where the expulsion of huge amounts of foam out of the bottle (ours lost half the bottle of liquid which is one litre of coke).
From research I have learnt that it is the chemical reaction between the potassium benzoate, aspartame and CO2 gas (that is contained in the Diet Coke) with the gelatin and gum Arabic ingredients of the Mentos which helps cause the formation of the foam that we see being produced.

Even though all these are factors of what causes this explosion of foam, scientists have learnt that it is the structure of the Mentos that is biggest cause.  Why?  Well it is believed that the surface of a Mentos mint is covered with many small holes, this means it has a larger surface area available for reaction and is what allows the CO2 bubbles to form so very, very quickly and such very, very large quantities of foam that is necessary for the projectile explosion that is much like a geyser in nature.
If you try this with a fruit-flavoured Mentos, with a much smoother surface that the mint version as it has a smooth waxy coating, and you'll find there's hardly a reaction which goes with the theory.

I read somewhere that rock salt can be used to jump start the reaction, another thing to try if you want to experiment further.

From Wikipedia:
A paper by Tonya Coffey, a physicist at Appalachian State University in Boone, North Carolina, goes into detail on the reasons and physics behind the reaction. Coffey found that the rough surface of the Mentos candy helps speed the reaction. Coffey also found that the aspartame in diet soda lowers the surface tension and causes a bigger reaction, but that caffeine does not accelerate the reaction.

For further fun experiments check out An Ordinary Life's Science page

1 comment:

  1. how can you use this experiment in real life? i really need to know ASAP!