💎 Grow Salt Crystals
Hang a string in a saturated salt solution and watch beautiful cubic crystals slowly grow over a few days!
🧰 What you need
Safety note: Ask an adult to boil the water. The jar will be hot — use oven mitts or let an adult pour.
🔬 Steps
- 1
Ask an adult to boil one cup of water. Pour it into the jar.
- 2
Add salt one spoonful at a time, stirring between each addition, until no more dissolves (the solution is now saturated).
💡 You'll know the solution is saturated when salt starts to pile up at the bottom even after stirring. - 3
Add a few drops of food colouring if desired. Let the liquid cool slightly.
- 4
Tie one end of the string to the middle of a pencil. Lower the string into the jar so it hangs without touching the bottom. Rest the pencil across the jar rim.
- 5
Place the jar somewhere undisturbed. Check it every day — crystals will start appearing in 24–48 hours and grow larger each day!
💡 Don't move or jostle the jar — disturbances can break small crystals as they form.
🧠 The Science
Hot water can dissolve much more salt than cold water. When you make a saturated solution (maximum salt dissolved), and then let it cool and evaporate, the water can no longer hold all the dissolved salt. The extra salt molecules have to go somewhere — they bond together in a very organised pattern and become solid crystals on your string. Salt crystals always form perfect cubes because of how sodium and chloride ions arrange themselves. This process is called crystallisation!
📚 Related Lessons
- 🏔️ Water Sources — Water comes from rivers, lakes, groundwater, rain, and dams — it travels a long journey to reach our taps!
- 🔄 Water Cycle — Water evaporates from oceans, rises as vapour, forms clouds through condensation, and falls as rain — endlessly!
- 🚰 Safe Water — Not all water is safe — germs, chemicals, and sewage contaminate water, but boiling, filtering, and chlorination make it safe!