DIY Science Experiment #13 - Crystal Geodes!
Geodes are small cavities in rocks lined with crystals and other minerals. You can make your own sparkling geodes using eggshells!
Materials: Clean eggshells, water, variety of soluble solids (table salt, rock salt, sugar, baking soda, epsom salt, etc), small heat proof containers, spoons, food coloring, mini muffin tins
- Crack the eggs for this project as close to the narrow end as possible. This preserves more egg to use as a container for the solution.
- Clean the eggshells using hot water. The hot water cooks the lining and allows you to pull the skin (egg membrane) out of the inside of the egg using your fingers. Make sure to remove all the egg membrane, if any membrane stays inside the shell it is possible that your eggshell will grow mold and your crystals will turn black.
- Use an egg carton lined with waxed paper or mini-muffin tins to hold the eggs upright.
- Use a saucepan to heat the water to boiling. .
- Pour half a cup to a cup of water into your heatproof container. If you poured half a cup of water into the container, add about a ¼ cup of solid to the water. Stir it until it dissolves. Likewise if you used a cup of water, add about ½ a cup of solid to the water. You wanted to add about half again the volume of the water as a solid to the mixture. When the initial amount of solid is dissolved continue adding small amounts of the solid until the water is super-saturated. Super-saturated simply means the water has absorbed all it is able to absorb and any solid you add will not dissolve.
- Add food coloring.
- Pour your solution into the eggshell carefully, filling it as full as possible without over-flowing it or causing it to tip. Find a safe place to put your shells while the water evaporates. Crystals will form inside of the eggshells as the water evaporates.
How does it work? Dissolving the crystals in hot water creates a super saturated solution. As the solution cooled, the water lost its energy and the crystals are forced from the solution to become a solid again. Since this happens slowly along with the evaporation, the crystals have time to grow larger than they were when the experiment started.
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