This project comes to us from Melissa Howard who is a Mom, Blogger, and photographer. This project nicely demonstrates how real-life geodes are formed in igneous and sedimentary rock. It also demonstrates super-saturated solutions and shows a nice variety of crystal shapes and formations.
YOU WILL NEED:
- clean eggshells
- a variety of soluble solids: table salt, rock salt, sugar, baking soda, Epsom salts, sea salt, borax, or cream of tartar
- small heat proof containers (coffee cups work well)
- food coloring
- egg cartons and wax paper or mini-muffin tins
WHAT TO DO:
- 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.
- Carefully pour your solution into the eggshell, 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 the eggshells as the water evaporates.
HOW DOES IT WORK?
Dissolving the crystals in hot water created what is called a “super-saturated solution.” This basically means that the salts took advantage of the energy of the hot water to help them dissolve until there was no more space between molecules in the 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. Natural geodes in rock are form in much the same way as mineralized water seeps into air pockets in rock. This is also how rock candy crystals are formed.
You can visit Melissa’s great blog and see more pictures HERE.
Amy Huntley is a former science teacher and Mom that runs a great blog where she shares activities that she has done with her family. This exploration of polymers and bouncing balls caught our eye and we were happy that Amy would share it with us. We’ve adapted it just a bit. The fun part is experimenting, and it is easy to make several of these and change up the recipe and check results. Note that this will not make a bouncy ball like you get at the grocery store, but ours bounced over a foot high and the ball has quite a unique feel to it.
You will need:
- Borax (found in laundry section)
- warm water
- corn starch
- glue (clear glue makes a see transparent ball and white glue makes an opaque ball)
- 2 small mixing cups
- a stirring stick (plastic spoon)
- food coloring (optional)
- Label one cup ‘Borax Solution’ and the other cup ‘Ball Mixture’.
- Pour 4 ounces (120ml) of warm water into the cup labeled ‘Borax Solution’ and 1 teaspoon of the borax powder into the cup. Stir the mixture to dissolve the borax.
- Pour 1 tablespoon of glue into the cup labeled ‘Ball Mixture’. Add 3-4 drops of food coloring, if desired.
- Add 1/2 teaspoon of the borax solution you just made and 1 tablespoon of cornstarch to the glue. Do not stir.
- Allow the ingredients to interact on their own for 10-15 seconds and then stir them together to fully mix.
- Once the mixture becomes impossible to stir, take it out of the cup and start molding the ball with your hands. The ball will start out sticky and messy, but will solidify as you knead it. Once the ball is less sticky, continue rolling between your hands until it is smooth and round!
“My boys loved making these “bouncy” balls. They are not super bouncy like the plastic super balls that became popular when I was a kid, but they are pretty bouncy and fun to play with. We discovered that on the carpet, they have a lot more bounce then they do on the kitchen floor. ”
These are also “temporary” bouncing balls and will lose their elasticity within a few days as they dry. Keeping your bouncy ball in a sealed bag will increase its bouncy lifespan.
The original “Super Balls” got their amazing bounce ability from compressed rubber under thousands of pounds of pressure.
How does it work?
This activity demonstrates an interesting chemical reaction, primarily between the borax and the glue. The borax acts as a “cross-linker” to the polymer molecules in the glue – basically it creates chains of molecules that stay together when you pick them up. The cornstarch helps to bind the molecules together so that they hold their shape better.
Make it an experiment
You can turn this activity into a true experiment by adjusting the amount of borax, glue, and cornstarch to get the highest bounce. You can also experiment to discover the best way to get the bouncy ball to keep its bounce over time. Have fun!
Check out Amy’s blog by clicking HERE.