Activities for Kids | Colors | Preschool | SAHM | Science
Colorful Crystals Science Experiment
It is the oldest thing on earth. A teeny (about the width of four human hairs), tiny zircon. This little zircon was part of earth’s crust and is thought to be 4.4 billion years old! (See a short clip here.) What is a zircon? It is a type of crystal. So are snow, salt, your beautiful diamond ring, and parts of your computer. Crystals are all around us and are used in countless ways. Their geometric shapes are beautiful and fascinating. Here is a simple experiment that allows you and your Littles to grow your own colorful crystals.
We began this experiment as part of a homeschool lesson about colors and the letter C. However, it can also be incorporated into lessons about geology, experimental design, evaporation, or solutes. It also works well as a “Nothing but Fun!” activity. (You know, that kind of activity where the kids think they are “just playing”, but we’re really sneaking in all kinds of interesting knowledge.)
What are Crystals?
Crystals are solids that have microscopic structures which are highly ordered. Their atoms make repetitive patterns that eventually form smooth, flat surfaces. The structure and shapes vary widely.
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| Crystals are solids with highly ordered microscopic structures. |
Did You Know: Some crystals have pretty
How to Do the Experiment
I had heard of growing crystals at home but hadn’t ever done it. When planning this activity, I read about crystal growing here, here, and here. We added our own twist and decided to set up a comparison experiment. We called it “Colorful Crystals.”
Materials
-Water
-Small pan for boiling (optional- you can mix without heating)
-3 home crystal substances/solutes (We chose alum, baking soda, and salt. Other options could be sugar, borax, or Epsom salt. This is where the experiment comes in. Some substances grow crystals while others don’t, and the crystals that form are of different structures.)
-3 clear cups
-3 pencils
-Yarn
-White board or paper for a sign
-Camera
–Free Printable Recording Sheet or make your own
Please have careful adult supervision and participation with this!
1.) Dissolve your first solute (example is salt or alum) in 3/4 cup water at a low boil or near boil. (Heat is optional.) Use as much of the solute as you can until it won’t dissolve anymore. This is a supersaturated mixture.
2.) Allow the mixture to cool enough that it won’t melt your cup. Pour the mixture into a clear cup and add food coloring of your choice.
3.) Set a pencil over the cup with a string tied to it that hangs down into the water.
4.) Repeat steps 1-3 with the other two solutes, making each a different color.
5) Write a sign that says “Day 1” (we used a small whiteboard) and take a picture of the whole set-up.
6) Talk about what you guess (hypothesize) might happen. Little #3 guessed that all of them will make crystals, but they will all look different. (The depth of the hypothesis will be age-dependent.)
Sidenote: While the crystals grow best with supersaturated mixtures, we only had two tablespoons of alum, which wasn’t enough to supersaturate our solution. In order to keep the other variables constant, we used only two tablespoons of each solute and 3/4 cup water, or as close to those as a four-year-old measuring gets. 🙂 You will get faster results than we did when you use more solute.
And Now, We Wait
Try not to disturb your crystals while you wait for them to grow.
Each morning change your sign and take a picture to see how the crystals change.
I have read that some results start to appear after a few hours. We saw definite changes after two days.
We decided to wait two weeks. Little #3 loved being in charge of this experiment, writing the number of the day, and taking the pictures.
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| It is hard to see the details in this picture, but crystals were growing on the sides and bottoms of the cups and on the yarn. |
Well, two weeks came and it was time to finish up our experiment. Little #3 cried. We calmed the tears and talked about our options. We decided to let the crystals grow longer.
So dinners came and went. Holidays came and went. Birthdays came and went. And our little crystals continued to grow.
I don’t know if it makes me crazy, lazy, or awesome, but that experiment sat on my kitchen counter for 65 days.
The Results
By 65 days, our water was almost completely evaporated, our crystals were as big as we thought they would get (debatably past their prime but nowhere near these giants), and we were both at peace about completing the experiment. 😉
Did You Know: Some of the biggest natural crystals
ever found are from a cave in Mexico and are
up to four feet wide by 36 feet long.
We were not disappointed with our results either!
Alum
The alum crystals were the first of our group to start forming. They were the largest of the three and grew mostly on the bottom of the cup.
Salt
The salt crystals formed all over the sides of the cup but most beautifully attached to the yarn. They were of tiny, perfect, cubic shapes.
Baking Soda
The baking soda crystals were the least definitively formed. They grew on the sides of the cup and in lumps on the bottom of the cup, as well as thickly on the yarn.
Shhh. Don’t tell Little #3, but one of the other Littles confessed to squeezing the cup, sending the first set of crystals back into the water. This could be part of why these crystals were kind of gloppy. (Gloppy is a word, isn’t it?)
Record Your Results
Record your results using this Free Colorful Crystals Printable. Alternately, you can make your own.
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| Age 4 |
This was a good way to incorporate some writing for Little #3. Older kids could write more and draw more detailed pictures of the crystal shapes.
Discuss
We had a fun time discussing our results. We talked about Little #3’s hypothesis…he was right! We talked about how the crystals grew (see below) and if there were other substances around the house that could grow crystals. Little #3’s favorite crystal was all of them and my favorite was alum. 🙂
Did You Know: Putting alum on a canker sore is
a great way to heal the sore.
You can find alum among the seasonings
at your grocery store.
Little #3 was really excited to put his crystals in bags and save them. He showed everyone in the family as well as everyone who came to visit.
Be aware that while many crystals are very strong, some of these that we made can be crushed or broken easily.
How Do These Crystals Form?
When the solute is dissolved in the water, the molecules of the solute break apart and become surrounded by water. Sometimes those molecules of the solute bump into each other or another object (like the yarn or cup in our experiment). When enough of them bump together, they stay together. This is called nucleation.
When that nucleus is formed, its outer edges have dangling bonds. Other nearby molecules attach to those bonds in the structural pattern specific to that solute. Eventually, the rough edges are filled with molecules, creating the smooth, flat surface of these crystals.
This site has some really helpful and simple pictures of the molecular process.
This whole process is sped up by evaporation. As the water evaporates, it leaves the molecules of the solute behind and searching for nearby bonds. We had a great discussion about evaporation as we asked, “Where did the water in the cup go?”
Your Turn
Now it is your turn to grow some incredible crystals! I hope you have fun and gain knowledge as you experiment with your Littles. Leave me a comment with any questions. Share pictures of your crystals using #lovinlifewithlittles. Be sure to Follow by Email to get even more insights, activities, and funny stories delivered to your mailbox from Lovin’ Life with Littles.
Have you already grown crystals before? Which solute is your favorite? I’m thinking of trying Borax and sugar next time. I wonder if any crystals would grow if you mixed the solutes? Any other suggestions that we should try?
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What a cool idea to compare the different crystals grown by different materials! : )