Mentos Lab - 8th Grade

The 8th graders just finished learning about the Layers of the Earth.  With this topic, we learned about how stress can build up within the earth and the pressure can become to great that sometimes the earth will explode (i.e. volcanoes).  With mentos and pop, there is a similar reaction, so we did performed the mentos lab!  

The Experiment: (Provided from http://www.stevespanglerscience.com)

1. You’ll need a 2-liter bottle of diet soda (diet doesn’t make a sticky mess) and an outdoor location for your geyser. Select a flat surface on the lawn or driveway to place the bottle.
2. Start by tying one end of the string to the trigger pin (the string might already be attached to the pin) on the Geyser Tube.
3. Open the bottle of soda and attach the Geyser Tube. Put the trigger pin into the hole at the base of the Geyser Tube.
4. Twist off the top cap on the Geyser Tube and drop MENTOS® candies into the tube. The trigger pin will keep the candy from falling into the soda before you’re ready. Replace the twist-on cap.
5. Warn everyone to stand back. Countdown… 3-2-1… and pull the trigger. The MENTOS will drop and the soda will go flying into the air!
6. Pour out the remaining soda and take a look at the MENTOS®. You can see where the soda has eaten away at the surface of the candy. No need to waste the candy… they still taste great.

The Photos:

 Audrey, Brie-anna, and Janessa were getting ready to watch the pop shoot into the air.  Janessa was one of the recorders for this lab.

Lindsey was getting ready to pull the plug on the mentos.  Sadly, we found that regular coke did not have a major reaction with the mentos.

This is the biggest reaction that we got!  It was with Diet Coke.  It went so high that I could not get the pop bottle in the shot with it. 

Alyssa had a misfire with her pop!  Her mentos fell into the pop a little too early, and she got soaked with Sprite! 

In the end, all of the students learned a lot and had a lot of fun!

The Explanation: (provided from http://www.stevespanglerscience.com)

"As you probably know, soda pop is basically sugar (or diet sweetener), flavoring, water, and preservatives. The thing that makes soda bubbly is invisible carbon dioxide gas, which is pumped into bottles at the bottling factory using tons of pressure. Until you open the bottle and pour a glass of soda, the gas mostly stays suspended in the liquid and cannot expand to form more bubbles, which gases naturally do.

But there's more... If you shake the bottle and then open it, the gas is released from the protective hold of the water molecules and escapes with a whoosh, taking some of the soda along with it. What other ways can you cause the gas to escape? Just drop something into a glass of soda and notice how bubbles immediately form on the surface of the object. For example, adding salt to soda causes it to foam up because thousands of little bubbles form on the surface of each grain of salt. Many scientists, including Lee Marek, claim that the Mentos phenomenon is a physical reaction, not a chemical one.

Water molecules strongly attract each other, linking together to form a tight mesh around each bubble of carbon dioxide gas in the soda. In order to form a new bubble, or even to expand a bubble that has already formed, water molecules must push away from each other. It takes extra energy to break this "surface tension." In other words, water "resists" the expansion of bubbles in the soda.

When you drop the Mentos into the soda, the gelatin and gum arabic from the dissolving candy break the surface tension. This disrupts the water mesh, so that it takes less work to expand and form new bubbles. Each Mentos candy has thousands of tiny pits all over the surface. These tiny pits are called nucleation sites - perfect places for carbon dioxide bubbles to form. As soon as the Mentos hit the soda, bubbles form all over the surface of the candy. Couple this with the fact that the Mentos candies are heavy and sink to the bottom of the bottle and you've got a double-whammy. When all this gas is released, it literally pushes all of the liquid up and out of the bottle in an incredible soda blast. You can see a similar effect when potatoes or pasta are lowered into a pot of boiling water. The water will sometimes boil over because organic materials that leach out of the cooking potatoes or pasta disrupt the tight mesh of water molecules at the surface of the water, making it easier for bubbles and foam to form."