ROCK CANDY CHEMISTRY: The Science Behind Crystallized Candy by Carly Vaughn, Digital Marketing Manager (2024)

Did you know that candy-making is really just a tasty form of chemistry? Next time you bite into your favorite sweet treat, consider the time and scientific experimentation that went into creating a shelf-stable, packaged candy that not only stays fresh but tastes AMAZING.

Learn more about the science behind your favorite Halloween treats, and find out how to create candy experiments of your own at home!

In general, candy is made by dissolving sugar into water to create a solution. Granulatedsugar, the most common type used in candy-making,is sucrose, a disaccharide molecule made up of glucose and fructose. When you force these two molecules to break apart, a very tasty reaction occurs: caramelization. The way that we force this reaction to occur is by adding heat into the mix when we try and dissolve sugar into water. Heating up the solution forces the sucrose molecules to break up and caramelize.

But when we do that, the sugar molecules really want to crystallize back into their solid form. Candy-makers use that crystallization process, and some strategic interference, to create the candies that we know and love.

The two basic categories of candy made this way:

  • Crystalline candies like rock candy and fudge.
  • Non-crystalline candies like caramels and marshmallows.

The key to mastering candy-making and creating amazing sweet treats is figuring out the concentration of sugar in your solution and the temperature that you need to heat it to. Lower concentrations of sugar are used with lower temperatures, since the more you heat your water the more sugar you can force to dissolved. Temperatures range anywhere from 223 degrees Fahrenheit to 350 degree Fahrenheit. Any higher and your sugar will burn (and taste bitter).

Itching to make your own candy at home? The most fun recipe to make is probably rock candy! Not only will you get to experiment with candy-making science, you’ll get to watch the formation of sugar crystals.

Homemade Rock Candy Experiment

Ingredients

  • 2 cups water
  • 6 cups granulated sugar
  • Optional: 1/2 to 1 teaspoon flavoring extract or oil – feel free to get creative!
  • Optional: food coloring – to give your candy a fun color

Equipment

  • 4 12-ounce jars or one quart-sized jar
  • Cotton thread & pencils or 4 wooden skewers
  • Candy thermometer

ROCK CANDY CHEMISTRY: The Science Behind Crystallized Candy by Carly Vaughn, Digital Marketing Manager (1)

The Experiment

  1. Clean your jars with hot water.
  2. For each jar, cut a piece of string that’s a few inches longer that the height of your jar and tape it to a pencil. Position the pencil over the mouth of the jar and wind it until the end of the string is hanging about an inch from the bottom. If you’re using skewers, use a clothespin to hang it in the jar.
  3. Bring 2 cups of water to a boil over medium high heat, then add one cup of sugar. Stir until it dissolves completely. Repeat this step with all 6 cups of sugar to create a supersaturated liquid. If your sugar is not dissolving, raise the heat.
  4. Heat the sugar solution until it reaches 230 degrees Fahrenheit on your candy thermometer. This is called the “soft ball” stage in candy-making.
  5. Remove the solution from heat and add flavorings (no more than 1 teaspoon).
  6. Carefully wet the strings or skewers in your syrup and roll them in granulated sugar. This will be the base of the sugar crystals.
  7. Optional: Add 6-7 drops of food coloring to your jars.
  8. Pour the sugar solution into your jars, leaving some room at the top.
  9. Position your strings or skewers in the clean jars as outlined in step 2.
  10. Let your jars sit undisturbed for 3-5 days. Watch your jars as candy crystals form! Make sure you don’t jiggle your jars too much. For larger candy crystals, put your jars in a dark warm room (or the back of the pantry).
  11. Finally! It’s time to enjoy some tasty candy!

Did you try this experiment? Tell us your results!

ROCK CANDY CHEMISTRY: The Science Behind Crystallized Candy by Carly Vaughn, Digital Marketing Manager (2024)

FAQs

What is the chemical change in rock candy? ›

A supersaturated solution is unstable—it contains more solute (in this case, sugar) than can stay in solution—so as the temperature decreases, the sugar comes out of the solution, forming crystals. The lower the temperature, the more molecules join the sugar crystals, and that is how rock candy is created.

What is a good hypothesis for rock candy experiment? ›

The hypothesis is that if sugar water is left to evaporate, sugar crystals will form on a string or stick, creating a rock candy treat.

What is the science behind candy-making? ›

In general, candy is made by dissolving sugar into water to create a solution. Granulated sugar, the most common type used in candy-making, is sucrose, a disaccharide molecule made up of glucose and fructose. When you force these two molecules to break apart, a very tasty reaction occurs: caramelization.

How long does the rock candy experiment take? ›

Most of the steps involve making the sugar syrup and preparing the sticks and jars. While you should start to see changes within the first few hours, it may take three to seven days for the rock candy to form.

Is crystalizing rock candy a chemical change? ›

Crystallization is a physical change by which one substance in a mixture separates itself from the mixture and forms solid, crystalline particles with other molecules of the same substance. If you've ever seen rock candy, or made it at home, you have seen the result of sugar crystallization.

What is crystallization in rock candy? ›

Crystallization in Candy-Making

If you use more sugar than water, as the syrup cools, sugar crystals can begin to form — this process is called crystallization.

What elements are in rock candy? ›

This activity helps students visualize how a supersaturated solution grows the extra-large crystals of sucrose needed to make rock candy. Table sugar (sucrose) and water are the only required ingredients. Food coloring and flavoring are optional ingredients to enhance the taste of the candy.

What is the dependent variable in a rock candy experiment? ›

Experiment for Growing Sugar Crystals Variables Dependent Variable: amount of sugar crystals collected Independent Variable: The independent variable is a part of the experiment that if changed could affect the dependent variable.

What is the independent variable in the rock candy experiment? ›

Independent Variable: The amount of sugar. We also separately tested mint flavoring extract. I observed that all the liquids were clear and that all sugar was dissolved. The red food coloring we used turned purple.

How does temperature affect the growth of rock candy? ›

Contrary to studies performed at an industrial level, we found that solutions heated to 90°C experienced significantly greater rock candy mass growth than solutions heated to 60°C, 70°C and 80°C. Additionally, solutions heated to 60°C, 70°C and 80°C experienced nonsignificant differences in mass growth.

What is the chemical formula for candy? ›

Did you know that most types of candy are made of sugar from two kinds of plants: sugar cane and beets? The common form of sugar is called sucrose (C12H22O11), a molecule made up from glucose and fructose (see front cover).

What are the 6 stages of candy making? ›

The Cold Water Candy Test
  • Thread Stage. 230° F–235° F. sugar concentration: 80% ...
  • Soft-Ball Stage. 235° F–240° F. sugar concentration: 85% ...
  • Firm-Ball Stage. 245° F–250° F. sugar concentration: 87% ...
  • Hard-Ball Stage. 250° F–265° F. sugar concentration: 92% ...
  • Soft-Crack Stage. 270° F–290° F. ...
  • Hard-Crack Stage. 300° F–310° F.

How does candy relate to psychology? ›

Help your Mood

Chocolate contains serotonin and phenylethylamine. These are natural antidepressants and can help stimulate your mood. Chewing gum has also been proven to reduce stress levels by lowering tension and releasing serotonin.

What is the science behind dissolving candy canes? ›

As the sugar and water molecules attract each other, they collide. At higher temperatures, there are more collisions because the molecules are bouncing around more and faster (see: kinetic energy), allowing the candy cane to break apart and dissolve faster.

What is the science behind melting candy? ›

The Science Behind It

The individual molecules of candies like M&M's are packed so tightly together that they can't move. That's why they're solid. When the candy molecules are warmed in the sun, however, they start moving around, making the candy melt into more of a liquid.

What is the science behind dissolving candy corn? ›

The Science Of Dissolving Candy Corn

Both water and sugar are polar molecules. When the candy corn is added to the water, the water molecules surround the candy molecules and pull them away from each other, making the candy disappear into the water.

What causes rock candy to grow? ›

As water evaporates from the string, small crystals of sugar will encrust the string. These tiny seed crystals provide starting points for larger crystals. Future growth will be concentrated around these points.

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