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 science behind the rock candy experiment? ›

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.

Is rock candy a mixture or solution? ›

Rock candy is a type of sweet, formed by the crystallization (meaning to form crystals) of large sugar crystals coming out of solution. This candy is formed by allowing a supersaturated solution of sugar and water to crystallize onto a surface suitable for crystal nucleation, such as a string.

Is there a chemical reaction in rock candy? ›

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.

What is the science behind candy? ›

The secret behind candy making lies in the skill of manipulating the inherent size and shape of a sugar crystal — more formally known as sucrose. As the compound is heated to different temperatures, it will move through several candy stages until the desired effect is achieved.

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

Independent Variable: The amount of sugar. We also separately tested mint flavoring extract.

What is your hypothesis for this experiment? ›

The hypothesis is an educated guess as to what will happen during your experiment. The hypothesis is often written using the words "IF" and "THEN." For example, "If I do not study, then I will fail the test." The "if' and "then" statements reflect your independent and dependent variables.

What is the crystallization separation technique rock candy? ›

Rock candy is made by dissolving as much sugar as possible into a pot of hot water, then cooling the sugar-water mixture to initiate crystallization. As the sugar-water cools, sugar molecules will separate out from the water and stick to other sugar molecules, forming solid crystals.

What is the process of sugar crystallization? ›

Crystallization takes place in a vacuum boiling pan. Thick juice or syrup is fed to the vacuum pans and evaporated until saturated. Seed crystals are added during a strike to grow sugar crystals.

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 solute and solvent in rock candy? ›

When you mixed the sugar with the water and then heated and stirred the solution repeatedly, you created a supersaturated solution. This means there are far more dissolved particles of solute (the sugar) than the solvent (the water) can normally dissolve and hold at a given temperature.

What is the science behind pop rock candy? ›

Pop Rocks® are sugar candies with tiny pressurized bubbles inside them filled with carbon dioxide gas. When you place Pop Rocks® in water, the sugar coating dissolves in water, and the gas and pressure are released. This also makes a popping noise, and leaves behind the sugar molecules.

What is the science behind the Skittles experiment? ›

The coloured sugar that is coating the skittles DISSOLVES in to the water and spreads out due to a process called DIFFUSION. The sugar will always move from the area where there is lots of sugar (next to the skittle) to a place where there is less, so you see the coloured sugar move across the plate.

What is the science behind candy chromatography? ›

The dyes used to make colored candy can be made up of several colors. These dyes are composed of different compounds that separate during chromatography. The water rising up the filter paper caused the compounds in the candy to spread out in a spectrum.

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