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Rock Candy: The Science Experiment You Can Eat!

Rock Candy—tasty sugar crystals on a stick to satisfy any sweet tooth, as long as you have the patience to make it! This fun science experiment is simple enough to do and requires very few ingredients.

 What you’ll need:

  • 1 Cup of Water
  • 3 Cups of Granulated White Sugarrbow rock candy 300x201
  • 1 Piece of Cotton String
  • 1 Pot and Stove
  • 1 Wooden Spoon
  • 1 Jar
  • 1 Paper clip
  • 1 Pencil
  • Food colouring or flavouring of your choice (this is an optional ingredient)It’s important to note that because this experiment requires the use of a stove, please ask an adult for assistance.

 Next steps:

The first thing you are going to do, is pour your cup of water and three cups of granulated white sugar into your pot. Make sure that you are constantly stirring your solution (with the use of your wooden spoon) until it begins to boil and until all of your sugar has dissolved.

If you decide to add food colouring or flavouring to your mixture, do so at this point.

Next, you will need your liquid to cool slightly; one of the simplest ways to do this is by putting your pot into your refrigerator. Don’t leave it in there for too long though!

What you need to do now is quickly prepare your jar and string for the mixture. Tie one end of your string to the middle of a pencil (the pencil should be long enough to cover the opening of the jar without falling in). Tie the other end of your string to a paper clip (this ensures that your string will stay straight when it is in the jar).

Test out the length of your string by placing the side with the paper clip inside the jar. The cotton string should be long enough to go almost the entire length of the jar, but without the paper clip touching the bottom.

Once you get the optimal length for your string, you will need to coat it. You can do so by dipping your string into the mixture that you have just put into your fridge. Then, allow your string to cool; this will form your first tiny crystals on the string.

Once your string has slightly hardened from the crystal sugars, place it back into your jar. Take out the remainder of your mixture from the freezer and pour it into your jar.

Now the hardest step is the wait. Place your jar aside on the counter somewhere, and wait patiently as the sugar in the solution attaches itself to the string. The waiting time can take between three days to a week, depending on how big you want your rock candy formation to grow! Once you notice that your candy has gotten big enough to your liking, then remove it carefully form your jar, and enjoy!

The great thing about this experiment is that you can make it different every time! Try different colours and flavours; see which combination you like best.

The science behind this delicious activity:

Water (a solvent—meaning it has the ability to dissolve other substances) can dissolve a certain amount of sugar. Note that sugar is a solute and can be dissolved in water.

When the water is heated up in the pot, it is able to dissolve more sugar than it would be able to at a cooler temperature. However, when your mixture begins to cool (when it is sitting on your counter), the water is unable to hold the amount of sugar it was able to hold before, when it was heated.

For this reason, the sugar crystals begin to latch onto the surface of the string, growing on top of the sugar that is already found on the string from when you coated it. The process is slow, but if you check on your jar enough, you can see amount of crystals on your string start to increase.

If you’d like, take a picture every 12 hours and see the progress of your creation!

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