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A classical explosion for a volcano is vinegar and baking soda. Occasionally, students may go outside and create another chemical volcano with diet coke and mentos candies. It can be messy but a fun way to ask students what is happening. You could build a learning cycle experiment around this demo/ lab. Have any of you done this? Resources: Tried and True: Using Diet Coke and Mentos to teach scientific inquiry Type: Journal Article http://www.youtube.com/watch?v=hKoB0MHVBvM http://wiki.ask.com/Diet_Coke_and_Mentos_eruption?oo=15147 http://www.newscientist.com/article/dn14114-science-of-mentosdiet-coke-explosions-explained.html How could you incorporate the learning cycle and this fun demo into your classes?

Hi Patty,
Yes, it has been written into a 5 E lesson format by some of my students in my science methods course. Each semester I have them choose a discrepant event and write the demo up in a 5 E format. The actual demo is usually the engagement phase of the inquiry lesson model.
An excellent resource for seeing how discrepant events can be written into a 5 E inquiry lesson plan model is this book chapter: Ten Activities for Middle School Science: Developmentally Appropriate, Inquiry- and Standards-Based
It provides 5 E lesson plans for 10 different discrepant events.
Carolyn

Hi Everyone - Great topic! This fun clip was on Blick on Flicks (NSTA) recently Coke Zero and Mentos Rocket Car - Mark II http://www.youtube.com/watch?v=g9DVuMtbsvo Here is a fun short video clip on Mentos & Diet Coke from Myth Busters http://dsc.discovery.com/videos/mythbusters-diet-coke-and-mentos.html Dorothy

My students did a science fair project on Mentos and Coke this year. They were trying to understand why the coke will explode so wildly when you throw in mentos and not other candies. It was a great experiment.

The issue with mentos and coke is that the rough surface (greater surface area) of the mento provides a place for the dissolved CO2 to aggregate - hence the eruption. Sodas with less dissolved CO2 do not work as well, nor do candies with smoother surfaces. Both are great variable to study. There is more CO2 in diet sodas to mask the unpleasant taste of artificial sweeteners. :(

Pam, thanks for the background information. This definitely would make a great science fair project using your suggested variables.

Thanks for the informaiton, Pam. The research we found called the tiny dents in Mentos, nucleation sites. The kids loved learning about the concepts that made the experiment work. We did not find out why the diet pop worked better so we thank you for that information especially.

Pam,
I have also heard that part of the increased reactivity may be due to differences in surface tension also. Don't know if it is true or not.

We carbonate our own water, and then add fruit juice to the bottles. I have found it interesting that the amount of CO2 released on the addition of the juice varies tremendously. Sometimes I get a volcano in my bottle, while other times it is just a little fizz. Cranberry juice is one of the less fizzy, while any of the less clear juices tend to be somewhat explosive - which I attribute to surface area differences. Also, if I add the carbonated water to the juice, it doesn't seem to be as explosive. These might be some fun kitchen experiments for more informal settings.

Also, for the volcano, we like to add stuff, but the students' favorites seem to be food coloring and dish detergent. Dish detergent adds viscosity, so there are more big 'lava' bubbles down the side of the volcano. Middle and elementary schools always like to add the color, even if not realistic, it helps them visualize the process even after the explosion because it stains the volcano. There is an interesting comparison of some of the alternatives at http://www.how-things-work-science-projects.com/erupting-volcano.html#salt, including a salt and soda volcano.

Thanks, Jennifer. I'm saving this for next year's science fair. Boy are we going to have fun.

Jennifer If the surface tension argument applies then the variation with juice might relate to the amount of sugar in the juice. The surface tension of water is due to hydrogen bonding. When sugar is dissolved in water some of the hydrogen bonding is "lost" as water forms hydrogen bonds to the hydroxyl groups of the sugar. So sugar reduces the surface tension and the more sugar the lower the surface tension. So does this hold for your data? Can you use the juice labels to determine the amount of sugar in each juice and use this to predict the degree of eruption? Cranberries are quite bitter. I believe that cranberry juice is often artificially sweetened with quite a bit of sugar. Another expansion of this project might be to have students determine the relative amount of sugar in each juice by density. The more sugar the greater the density the less the eruption. If one wanted to get more quantitative then have students create a standard density curve using solutions with known varying sugar quantities and then comparing the juices to the standard curve.

So Pam, Is it the reduced CO2 or the increased sugar that makes sugar sodas less explosive than diet?

The two are related. A reduction in surface tension mean less dissolved CO2 and then less eruption.

Thanks, Pam.

Great analysis (and extension)! I wonder if "real sugar" sodas have different reactions than those sweetened with high fructose corn syrup?

I will try the corn syrup vs sugar pop for an end of the year test. It will be great for my kids to follow up on what they did before.

You may not have heard of chemical volcanoes before, but they are a pretty interesting concept. When you hear the word 'volcano,' what comes to mind? Most people think of an explosive eruption of ash and lava, but chemical volcanoes are a little different. A chemical volcano is a type of volcano that is created when a gas-rich magma chamber is pressurized by the surrounding rock. I am to read https://coworkingmag.com/magazine/how-to-choose-the-best-dissertation-writing-service/ article for help in my essay. When the pressure builds up, chemicals and gases that are dissolved in the magma come out as a gas. This gas can then be ignited when it comes into contact with oxygen.