Science: Rock Candy

 Hi there! 

Today I will be writing about how I made Rock Candy at home during lockdown. 

Aim: Make rock candy at home

Method: 

(Note: make sure you have a 3:1 ratio of sugar and water, I will be using 3 cups of sugar and 1 cup of water.)

1. Combine equal parts of sugar and water in a saucepan and heat.

2. Slowly add more and more sugar and mix until it doesn't dissolve any more. The water will start to look a little cloudy, this means no more sugar will dissolve. You can double or triple the recipe if you want, as long as a 3:1 ratio remains. At this point, you can also add flavouring or food colouring if you would like. Remove from heat and let cool.

3. Cut skewers to a desired size (which fits in the jar you will use), then dip them in water and then in sugar. Set them aside and allow to dry fully. 

4. Once the sugar-water mix has cooled down enough, pour it into jars (or whatever you are using). Once the sugar dipped sticks are dry place them in the jar. They must be fully dry, if they aren't, when you place them in the jar the sugar will dissolve. Also, make sure the skewers aren't touching the sides or bottom of the jar. 

5. Let it sit for a couple of days or as desired and you can eat the rock candy. Once you take them out, let them dry and enjoy!

Results:

Day of making:

Discussion:

When the water and sugar are heated together, it creates something called a 'supersaturated solution'. This means there are way more particles of dissolved sugar/solute than water/solvent is normally able to dissolve at a regular temperature. By stirring sugar in hot water, the sugar dissolves faster in the heated/fast-moving water molecules.

As the water cools down, the large amount of sugar particles remains in the supersaturated solution, meaning there's now more sugar than can actually stay in the liquid. This leftover sugar falls out of the solution as particles. They connect with other sugar particles and a rock candy crystal will start to grow. 

The sugar-dipped skewer is a key part in actually getting the crystals growing. The dried sugar acts as 'seed' crystals when you place it in the supersaturated solution. As all the sugar particles start to settle, they join together, forming crystals with other molecules of sugar. You can see this crystallisation happen on the sides and bottoms of the jar, and of course on the skewer. Until you take out the skewer, the molecules of sugar will continue to crystallise on the string and other crystals giving you rock candy.  

Conclusion:

I really enjoyed this experiment. Unfortunately, for me it didn't work on my first attempt so I tried again and it worked. However, crystals grew everywhere in the jars I used apart from the skewers which I found funny. Even if they didn't end up growing, I liked checking on the skewers everyday in the morning.

Thanks for reading!