Crystals Demonstrations
Crystals are solids in which particles are arranged in regular, repeating patterns. This category explores how crystals form, the conditions that influence their growth, and the structures they create. Studying crystals provides insights into the organisation of matter and connects to topics in chemistry, geology, and materials science.
| Demonstration | Materials | Difficulty | Safety | Summary |
|---|---|---|---|---|
| Copper Sulfate Crystals | ★★☆ | ★☆☆ | ★★☆ | A perfect seed crystal is grown in a shallow dish, then suspend the seed in a saturated, undisturbed solution so it enlarges slowly into a clear, well-formed single crystal. Careful control of saturation, evaporation, and disturbances is the key to size and quality. |
| Making Light by Rubbing Quartz | ★★★ | ★☆☆ | ★☆☆ | In a dark room, rub or strike two pieces of clear quartz together to produce brief flashes of light and a faint odor. This visible glow is triboluminescence - light emitted when crystals are stressed, fractured, or rubbed. |
| Salt Crystal Garden | ★★★ | ★☆☆ | ★☆☆ | Grow delicate salt crystal structures on a porous base by wicking a salty bluing solution upward and letting it evaporate. Optional ammonia speeds evaporation, while the bluing particles act as nucleation sites that help crystals form quickly. |
| Borax Crystal Snowflakes | ★★☆ | ★★☆ | ★★☆ | Make snowflake ornaments from pipe cleaners by growing borax crystals from a hot, supersaturated solution. Compare color methods (colored pipe cleaners, food coloring, or post-painting with watercolors) and observe how crystals form and how color moves through the crystal structure. |
| Epsom Salt Crystals | ★★☆ | ★★☆ | ★★☆ | Dissolve magnesium sulfate heptahydrate (“Epsom salts”) in very hot water to make a saturated solution, then pour into shallow dishes and let cool undisturbed so long, slender crystals grow. Compare growth at room temperature versus in a refrigerator and extend the activity using seed crystals. |
| Evaporating Seawater | ★☆☆ | ★★☆ | ★☆☆ | Dissolve table salt in warm water to make a saturated solution, then leave the solution in a shallow container for days. As water evaporates, the remaining liquid becomes supersaturated and salt recrystallizes on the dish and along the waterline. |
| Golden Rain | ★★☆ | ★★☆ | ★★☆ | Lead nitrate reacts with potassium iodide to form a bright yellow precipitate of lead iodide. When heated, the precipitate dissolves in hot water, but as the solution cools, thin hexagonal crystals fall out of solution like golden flakes, creating the “golden rain” effect. |
| Grow Egg Geodes | ★★☆ | ★★☆ | ★★☆ | Empty and clean eggshell halves are coated with glue and alum powder, then soaked in a hot, colored alum solution so clear alum crystals grow inside the shells, forming geode-like ornaments within a day. |
| Growing Crystals on String | ★☆☆ | ★★☆ | ★★☆ | Dissolve table salt (or epsom salts) in warm water until no more will dissolve, then suspend a paper-clip “seed” on a string into the solution and leave it undisturbed for about a week. As water slowly evaporates, the solution becomes supersaturated and sodium chloride crystallizes, often as tiny cubes on the seed. |
| Rock Candy | ★★☆ | ★★☆ | ★★☆ | Dissolve sugar into hot water until it forms a supersaturated solution, then suspend sugar-coated sticks in jars to grow edible sugar crystals over several days. Color or flavor can be added to make decorative, tasty rock candy. |
| Silver Nitrate Christmas Tree | ★★☆ | ★★☆ | ★★☆ | Branching silver crystals are grown on a copper “tree” by immersing the copper in a dilute silver nitrate solution. A single-displacement redox reaction plates metallic silver onto the copper while the solution turns blue from copper(II) ions. |
| Crystallization of Sodium Acetate | ★★☆ | ★★☆ | ★★☆ | A hot, concentrated solution of sodium acetate trihydrate is cooled quietly to create a supersaturated liquid. When poured onto seed crystals, it crystallizes instantly to build a warm, solid tower. |
Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories
Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher
Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff