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Mentos Diet Coke Geyser


  • A roll or box of Mentos mints
  • 2-liter bottle of diet soda (diet or regular soda will work, but diet soda is not as sticky)
  • Piece of paper (or for a perfect drop every time, check out Steve Spangler’sGeyser Tube)


  1. This activity is probably best done outside in the middle of an abandoned field, or better yet, on a huge lawn.
  2. Carefully open the bottle of soda. Position the bottle on the ground so that it will not tip over.
  3. Unwrap the whole roll of Mentos. The goal is to drop all of the Mentos into the bottle of soda at the same time (which is trickier than it looks). One method for doing this is to roll a piece of paper into a tube just big enough to hold the loose Mentos. You’ll want to be able to position the tube directly over the mouth of the bottle so that all of the candies drop into the bottle at the same time.
  4. Don’t drop them into the bottle just yet! Warn the spectators to stand back. Okay, you’re going to drop all of the Mentos into the bottle at the same time and then get truckin’ (move out of the way… so long… bye- bye… hasta la vista!)
  5. It’s just like fireworks on the 4th of July. The spectators erupt, of course, in a chorus of ooohs and ahhhs. Someone yells out, “Do it again” and you do.

The Geyser Tube Variation

  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 7 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.

 What are they learning

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.

Easy Bubbly Colours Experiment

What you need

  • 4 large tablespoons of bicarb soda (or baking powder)
  • 1 cup white vinegar
  • 4 different food colourings (‘natural’ ones are not concentrated enough so stick to the evil chemical version)
  • Muffin tin
  • Teaspoon



Ideally, set this experiment up outside, because to make it work properly it has to get a bit messy and bubble over.
Depending on how many colours you have, use a different muffin cup for each colour.
We used four colours.
So start by half-filling each muffin cup (in our case four muffin cups in total) with vinegar.
Now put one drop of each colour into a different cup of the muffin tin.
Now plonk one heaped teaspoon of bicarb into each cup and watch the colours fizz!

What are they learning?

This simple kitchen science experiment is a fun learning activity. Combining vinegar and bicarb makes all sorts of oozing bubbling reactions. Add some colours and you’ve got one cool science experiment! Watch the video tutorial to show you how to create it.

The acetic acid in the vinegar reacts with the sodium bicarbonate to form carbonic acid.

The carbonic acid is unstable and immediately falls apart into two components of carbon dioxide and water. The carbon dioxide escapes the water as gas. It bubbles up and then, because it’s heavier than air, it sort of falls down again, flowing like water over the edges of your muffin tin.

Monster toothpaste science experiment

What you need

  • sheets of newspaper (to catch the mess)
  • 1 x empty soda bottle
  • 1 x tsp yeast
  • 2 x tbs warm water
  • a plastic funnel (to stop spillage)
  • 1/2 cup hydrogen peroxide (at least 6 percent, available at pharmacies)
  • 4-5 drops of food colouring
  • a squirt of dishwashing liquid


Place the empty bottle in the centre of the sheets of newspaper.
In a small jug mix together the yeast and warm water. Agitate it until bubbles form (you need to activate the yeast).
Use a funnel to pour 1/2 cup of hydrogen peroxide into the soda bottle. Add some food colouring and a squirt of dishwashing liquid.
Now add the yeast mixture to the bottle.
Watch the monster toothpaste rise up and ooze out of the bottle.

Why are they learning?

Big messy science experiments are a fun way to get your kids interested in how things work. This ‘monster toothpaste’ science experiment for kids is a great hands-on learning activity.

Hydrogen peroxide naturally breaks down into water and oxygen. The yeast speeds up the reaction. Dish soap catches the oxygen particles as they are released by the ‘breakdown’ process and forms bigger bubbles. The foam and the bottle feel warm because it is an ‘exothermic’ reaction: meaning it releases energy as heat.