Monday, February 20, 2012


Science Experiment: Diet Coke and Mentos Geyser

My preschoolers love experimenting with reactions, and the classic Diet Coke and Mentos reaction is so popular it's been requested and repeated more than once!

The INGREDIENTS are simple:
  • Diet Coke (you will want several bottles!)
  • Mint-flavored Mentos  (at least two rolls!)
  • Other mix-ins  (rock salt, nails, and other candy are interesting ones, but let your child choose what she wants to experiment with!)
The HOW TO is fun:

1.  Plan how you will put 5 Mentos into a 2-liter bottle of Diet Coke at the same time.  I've used a roll of paper, but prefer to thread them onto a string with a needle.  It doesn't take long to thread, and is so much more effective.

2.  Drop 5 mint-flavored Mentos into a 2-liter bottle of Diet Coke at the same time.  Step back fast!

3.  Oooh and aaah!!  Note: the reaction only lasts 5-6 seconds, and the kids usually want to do it again...and soon!

4.  Talk about the reaction on whatever level your child can understand.  Then invite her to experiment with other reagents.  Is there anything else that makes as big a reaction as the Mentos/Diet Coke combination?
What does make the reaction?  Interestingly enough, there is still considerable debate about the cause (it's even been on Mythbusters!), but this is the most likely explanation.  As you know, Diet Coke is a very carbonated drink.  The molecules of carbon dioxide (a gas) are surrounded by molecules of water.  The surface tension of water is quite strong (strong enough for insects and even the basilisk to run across the top of water!), but there are lots of ways to break it.

If you shake the bottle before you open it, you release a lot of carbon dioxide that will rush out the top of the bottle when you open it.  When you drop certain objects (or candy) into the drink, you also break the surface tension and release carbon dioxide.  Mentos contain gum arabic and gelatin that seem particularly effective in breaking the surface tension.  Mint Mentos are especially exciting because they have many little holes on their surface (called nucleation sites) that the carbon dioxide will cling to, making the reaction even more explosive!  Fruit-flavored Mentos do not have the nucleation sites (you can feel how smooth they are), and do not make nearly as exciting a reaction.

So, to summarize, the Diet Coke/Mentos reaction seems like a physical reaction, not a chemical reaction.  The final products are the same as the initial ones, but they combine to form a geyser that is fun and exciting!

I'll be sharing this post at some of these linky parties!
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Michelle said...

I used the elephant toothpaste experiment with my four year olds for our science class. What a hit! The children loved it! I tried it out first with my own 11 year old and she wanted to do it over and over. Thank you for posting this experiment. It is sometimes hard to find new things to try with younger children

Carla at Preschool Powol Packets said...

Hi Michelle! I'm so glad you were able to enjoy it at home and school! Thank you so much for letting me know! I hope you continue to find useful ideas here!

Janice said...

Fun! We saw this done at the AZ State Fair a few years ago as part of a huge performance. It was amazing! Thanks for linking up at Family Time Tuesday!

Carla at Preschool Powol Packets said...

Janice, that sounds like fun! This is one my kids love doing, and...I'll admit...I enjoy the fountain in the backyard too!

Mama Jodi said...

This is one of my husband's favorite activities. I'll have to remember to do it with my own preschoolers.

Carla at Preschool Powol Packets said...

Mama Jodi, I love how it is as much fun for the "grown-ups" as for the kids!

Kristie said...

I've heard of this but haven't done it yet...and I love your explanation! I hope you don't mind that I pinned it so I can do it in the future. Thanks for sharing!

Carla at Preschool Powol Packets said...

Thanks so much for pinning this, Kristie!

Shiloh said...

I've seen this done, and it's always SOO much fun.:)

Carla at Preschool Powol Packets said...

I completely agree Shiloh! It never gets old!

CacheyMama said...

Thanks for linking up at Thinky Linky Thursday this week! We are happy to have your ideas.
Lori @ Cachey Mama’s Classroom

andie jaye said...

this has been on my to-do list for forever! such fun, huh? thanks for linking up to tip-toe thru tuesday!

Carla at Preschool Powol Packets said...

Lori, I love Thinky Linky!

Andie Jaye, I'm so glad I found tip-toe thru tuesday!

Charlene@APinchofJoy said...

Thanks for linking to Busy Monday at A Pinch of Joy! Great idea to string the mentos together! Good explanation of the experiment, too. Pinned this. Can't wait to see what you have for this week's party!

Jamie H said...

I LOVE doing this experiment! Thanks for linking up to Fun Stuff Fridays!

CacheyMama said...

Congrats, this post has been featured on Thinky Linky Thursday. Go to my blog to see and get your “featured” button!
Lori @ Cachey Mama’s Classroom

Carla at Preschool Powol Packets said...

Thanks, Charlene!

Me too, Jamie!

Lori, That's awesome! Thanks!