Crystal Growing Science Experiment
Grow crystals from a saturated sugar or salt solution over several days. Watch as invisible molecules organize themselves into glittering geometric structures.
What You'll Need
- 1Sugar (about 3 cups) or table salt
- 2Water
- 3Clean glass jar
- 4String or cotton yarn
- 5Pencil or stick for suspending string
- 6Food coloring (optional)
- 7Paper towel for covering
What You'll Need
Sugar (about 3 cups) or table salt
1 cup water
A clean glass jar
String or cotton yarn
A pencil for suspending the string
Food coloring (optional)
Paper towel for covering
How to Play
Boil water (adult help). Add sugar slowly, stirring, until no more dissolves.
Pour the saturated solution into a clean jar.
Tie string to a pencil and dangle it in the solution.
Add food coloring for colored crystals if desired.
Cover loosely. Place somewhere undisturbed.
Check daily. Small crystals appear in 2-3 days.
After 5-7 days, pull the string out and examine the crystal structure.
The Science Behind It
When you dissolve sugar in hot water, the heat allows more sugar to dissolve than cold water could hold. As the solution cools, it becomes supersaturated — there's more sugar dissolved than the water can actually hold at that temperature. The excess sugar molecules start connecting to each other in organized patterns, forming crystals. The longer you wait, the bigger they grow.
Tips
Use a rough string (cotton yarn works well). Smooth surfaces don't nucleate crystals as easily.
Don't move or bump the jar once it's set. Vibration disrupts crystal formation.
Sugar crystals take longer but are larger and more dramatic. Salt crystals form faster but are smaller.
The jar must be clean. Impurities cause cloudy or irregular crystals.
Try growing crystals on different surfaces: a pipe cleaner, a rock, a wooden stick. Compare results.
Keep a photo journal of the crystal growth each day. The progression from invisible to massive is the story of molecular self-assembly.
Frequently Asked Questions
How long does this activity take?
This activity takes about 30 min, with 10 min of preparation time beforehand.
What materials do I need?
You'll need: sugar (about 3 cups) or table salt, water, clean glass jar, string or cotton yarn, pencil or stick for suspending string, and 2 more items.
What age is this activity for?
This activity is designed for 8-12 years. You can adapt it for younger or older children by adjusting the complexity.
Can this be done indoors?
This activity is designed for indoor play, making it perfect for rainy days or when you're staying inside.
How difficult is this activity?
This activity has a moderate difficulty level. It may require some preparation or guidance, but is manageable for most families.
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