Candy Chemistry Experiments

There are a lot of science discoveries to make using your favorite candy. Just don't eat the lab tools!

As a rule, playing with with your food is not a cool idea. However, candy isn’t really a food and you aren’t really playing with it as much as exploring it. Besides, how are you supposed to wonder, discover, and explore if you can’t play? Hit the candy cupboard for some kitchen-science lessons in solubility, buoyancy, and chemical reactions.

Mentos is a registered trademark of Perfetti Van Melle Benelux B.V.
Geyser TubeTM is a trademark of Steve Spangler, Inc. All rights reserved.

Experiment Materials

  • Mentos® Geyser Tube™
  • Demo Tank (or deep bowl)
  • Various candy bars (SNICKERS®, 3 Musketeers®, Kit Kat®, and HERSHEY'S® Chocolate Bars, etc.)
  • Gummi™ (or Gummy) Bears
  • Ruler, digital cooking scale (optional)
  • Mentos® original candy
  • Soda (all brands, both diet and regular)
  • Cups or glasses, 9 oz (266 ml)
  • Salt
  • Granulated sugar
  • Water
  • Paper towels
  • Adult supervision

Experiment

1

Float or Sink Candy Bars

An object’s density causes it to sink or float in water. What will your favorite candy bars do?

  1. Choose several of your favorite candy bars like SNICKERS, 3 Musketeers, HERSHEY’S Chocolate Bars, Kit Kat, etc.
  2. Fill a deep bowl (or the demo tank) with room temperature water.
  3. Remove the wrappers from the candy bars and place them into the water. (No fair taking a bite from one!)
  4. The HERSHEY’S and SNICKERS sink like rocks to the bottom, while the Kit Kat and the 3 Musketeers bars float at or near the surface. Explain what happened in terms of “density.”

How does it work?

A Kit Kat bar has a lot of empty space in between the chocolate and the wafer cookies. Those pockets contain air, which help keep the density low so the bar floats. The same is true for the 3 Musketeers bar. The nougat center has a lot of tiny air bubbles whipped into it, creating little pockets of air to keep the density low so it floats on the surface of the water, too.

Like a 3 Musketeers, the SNICKERS has a whipped nougat center but the pockets of air it contains aren’t enough to overcome the higher density of the peanuts, caramel, and chocolate. HERSHEY’S bars have the same problem. There are a few air pockets in the solid chocolate, but not enough to keep the bar from sinking.

Take It Further

Cut the bars in half (either way) to see what’s inside and to test whether or not having the water contact the inside of a bar makes a difference. You probably found that the exposed side didn’t make a difference to the buoyancy of the bar. It’s likely that the numerous air pockets inside were simply too small for the water to effect.

Test other types of bars or plain candy to see what floats or sinks. Before placing one into water, do a little “research” by biting into the candy and to see what’s inside. Make an educated guess (a hypothesis) based on the contents as to whether the candy will float or sink.

2

Incredible Swimming Gummi Bears

Some candies dissolve in water, some get bigger, but who knows what Gummi Bears will do?

  1. Measure and weigh nine Gummi (Gummy) Bears first. Use a data table to record your findings.
  2. Fill three glasses or cups  with room temperature water.
  3. Leave the water plain in one cup, add a tablespoon of salt to a second cup, and a tablespoon of sugar to the third cup.
  4. Place three measured and weighed Gummi Bears into each cup.
  5. Wait 12 hours (or overnight) and measure and weigh the bears again. Put them back into the same cups.
  6. Check back after 24 hours, measure and weigh the bears again, and put them back.
  7. Check back after 48 hours, measure and weigh the bears a third time.

How does it work?

Most sugary candies dissolve when left in water. Even the candy bars used in the Sink and Float activity began to dissolve after a short time in water (not a pretty sight!). Why do the Gummi Bears get larger instead of dissolve in the water? The secret is gelatin – one of the main ingredients in the candy bears.

When they’re made, gelatin and water are heated and mixed, just like making a gelatin dessert. As the mixture cools, water leaves the candy and it hardens to a chewy texture. Gelatin is a long, chain-like molecule that twists and forms a solid. As the water is removed in the cooling process, the gelatin reconnects with itself.

When Gummi Bears are in water, water molecules (the solvent) move into the bear by means of osmosis. That is, water molecules cross a semi-permeable membrane (the gelatin allows the water through) into an area of higher solute (the gelatin) to equalize the solvent (the water) concentration on both sides of the surface of the candy.

So what does that mean? At the start, there is less water and more gelatin inside the Gummi Bear. To equalize things, water molecules are drawn into the candy where there are fewer water molecules and a lot of gelatin molecules. The gelatin makes the Gummy Bear act more like a sponge by absorbing water instead of being dissolved in it.

Why does salt dissolve in water and gelatin doesn’t?

A solute is a substance dissolved in another material. When salt is dissolved in water, the salt is the solute and the water is the solvent.

Salt is not formed from chains like gelatin and gelatin molecules are much larger than salt molecules.

What happens when you add salt or sugar to the water?

Salt or sugar ions in water are much smaller than the gelatin molecules in the candy. Salt water has about 10-20 times the molecules than what is in the Gummi Bear. Because of osmosis, water molecules move to an area with more solute in it to balance things. The catch is that the water is locked up in the candy and can’t move. The Gummi Bear can’t shrink further, so it stays about the same size.

Adding sugar to water has the same effect as the salt.

Test this yourself. What happens to the Gummi Bears when you soak them in tap water and in distilled water? How do you get different results by using another solvent instead of water? What about soda?

Safety note: do not eat the Gummi Bears after they have soaked in water. When you handle them with your fingers and then drop them back into the water, something else is added and begins to grow – bacteria!

Soda Geyser

3

Which Liquid Creates the Highest Mentos Geyser?

Room-temperature Diet Coke is the preferred soda when erupting Mentos soda geysers, but is it really the best?

Use this science fair project to determine which soda makes the best geyser.

Take a trip to your local grocery store and study the soda aisle. Observe several different types, flavors, and brands of soda. Purchase two of each you want to test because you’ll want to run your experiment twice for the sake of scientific accuracy. While you’re at the store, better buy several rolls of Mentos original candy, too.

Find a good, flat location outside, like a building wall and mark off measurements using a tape measure up the wall. You want to easily detect which geysers will go the highest and which ones will fizzle.

Drop the same number of Mentos candies into each soda, one at a time, and note the height. A Mentos Geyser Tube makes this very simple.

You may be surprised at which sodas shoot the highest. Can you figure out a common thread among the best and worst geysers?

Take this experiment to the next level and check out all of the science fair ideas for the Mentos Geyser here!