In this activity we are going to explore how crystals are made by making some edible sugar crystal sticks! This activity takes a few days to complete so is perfect for an at-home Science Week experiment!
You will need:
- Measuring cup
- 6 plastic cups
- Food colouring
- Kebab or lolly sticks
- Clothes pegs
- String (optional)
- Add 3 cups of sugar and 1 cup of water then stir until dissolved, then add any food colouring of your choice.
- Make sure your sugar has fully dissolved, then leave to cool for a few minutes before adding it into the plastic cup. Then get your stick and insert the end in the middle of a clothes peg, then clip another clothes peg at the end of the first peg. Place the stick in the sugar solution with the pegs lying across the top of the cup.
- Check the progress of the crystal formation every day. After two days you should see some results! At this stage, you will need to lift the top layer of sugar that has formed on the surface of the mixture with a fork or spoon, and remove the stick. You can throw away the top sugar layer but keep all the sugar crystals that have formed on the stick. Transfer the mixture to a fresh cup and replace the crystal stick in the solution.
- Repeat step three every couple of days until your sugar crystals are your desired size. The crystals on the stick will grow as the sticky, gooey sugar solution slowly decreases.
- When you're happy with the size of the crystals leave them out to dry on a plate and store somewhere dry for 2 days.
- Enjoy your sugar crystals! You can eat them or tie string around them to make them into an ornament!
How did the sugar crystals form on the stick?
Sugar can be dissolved in water to make a solution where water molecules and sugar molecules are mixed together as a liquid. Over the days when you left your sticks in the sugar solution some of the water molecules evaporated meaning that there was less water in your solution to mix with the sugar. The sugar molecules in the solution join together when they bump into each other and start to form crystals. Crystals form best when there is a surface to grow on, such as the surface of the solutions (the sugar layer you had to remove) or the stick in the solution. Sugar molecules continued to join on to the crystals, like building blocks, until the end of the experiment when you removed the crystal stick from the solution.