Growing crystals is actually pretty easy to do at home and makes a great science and chemistry experiment for kids. This growing borax crystal hearts experiment for Valentine’s Day makes a great science activity and decoration to try with kids. We have tons of fun Valentine science experiments you are sure to love!
Valentine’s Day Science
This borax crystal heart science experiment is a set-it-up-and-forget-about-it kind of experiment like our crystal snowflakes. Growing crystals is a classic science experiment that you must try with your kids!
You can get creative and make any shape for your crystals to grow! Here are a few of our favorites…
Make sure to check out the video below and see it in action.
Crystal Hearts Experiment
NOTE: Adult assistance will be needed. Since you are dealing with hot water, my son watched the process while I measured the solution and stirred it. Borax is also a chemical powder best used by an adult for safety.
If you want a more hands-on type of crystal experiment, try our salt crystal hearts.
- Jars or vases (glass jars are preferred over plastic cups)
- Popsicle sticks
- String and tape
- Pipe cleaners
CRYSTAL HEARTS SET UP
STEP 1: Take your pipe cleaners and form them into hearts! Twist two different colors together! Or you can entwine two hearts!
Hint: Double-check the jar’s opening with the size of your shape! It’s easy to push the pipe cleaner in to start but challenging to pull it out once all the crystals have formed! Make sure you can get your heart in and out easily!
STEP 2: Use the popsicle stick (or pencil) to tie the string around. I used a small piece of tape to keep it in place. You can do two hearts in one jar, but make sure they are small and have room! They would also look pretty if they grew together!
STEP 3: MAKE YOUR BORAX SOLUTION
The ratio of borax powder to boiling water is 3:1. You want to dissolve three tablespoons of borax powder for each cup of boiling water. This will make a saturated solution, which is a great chemistry concept.
Since you need to use boiling hot water, adult supervision and assistance are highly recommended.
STEP 4: Make sure the heart is fully submerged in the solution!
The crystals are growing!
You want to set the jars in a quiet place where they won’t be disturbed. No tugging on the string, stirring the solution, or moving the jar around! They need to sit still to work their magic.
After a couple of hours, you will see some changes. Later on that night, you will see more crystals growing! You want to leave the solution alone for 24 hours.
Make sure to keep checking to see the stage of growth the crystals are in!
The next day, gently lift out your crystal heart ornaments and let them dry on paper towels for an hour or so…
The Science of Growing Crystals
Crystal growing is a neat chemistry project that is quick to set up and involves liquids, solids, and soluble solutions. Because there are still solid particles within the liquid mixture, the particles will settle to form crystals if left untouched.
Water is made up of molecules. When you boil the water, the molecules move away from one another. Boiling hot water allows more borax powder to dissolve to create the desired saturated solution.
You are making a saturated solution with more powder than the liquid can hold. The hotter the liquid, the more saturated the solution can become. This is because the molecules in the water move farther apart, allowing more of the powder to be dissolved. If the water is colder, its molecules will be closer together.
Do you love chemistry… make sure to check out all our chemistry experiments!
As the solution cools down, there will suddenly be more particles in the water as the molecules move back together. Some of these particles will start to fall out of the suspended state they were once in.
The particles will then settle on the pipe cleaners and the container and form crystals. Once a tiny seed crystal is started, more falling material bonds to form bigger crystals.
Crystals are solid with flat sides and symmetrical shapes and will always be that way (unless impurities get in the way). They are made up of molecules and have a perfectly arranged and repeating pattern. Some might be bigger or smaller, though.
Let your crystal hearts work their magic overnight. We were all impressed by what we saw when we woke up in the morning! We had quite the pretty crystal hearts Valentine’s science experiment!
Go ahead and hang them in the window like a suncatcher!
Growing Crystals in the Classroom
We made these crystal hearts in my son’s 2nd-grade classroom. This can be done! We used hot water but not boiling from a coffee urn with a spout and plastic, clear party cups. The hearts needed to be smaller or fatter to fit in the cup.
Plastic cups are generally not recommended for growing the best crystals, but the kids were still fascinated by crystal growth. When you use plastic cups, the saturated solution can cool too quickly, leaving impurities to form in the crystals. The crystals will not be as sturdy or perfectly shaped. If you can use glass jars, you will have better results.
Also, you need to make sure the kids really don’t touch the cups once they have gotten everything together! The crystals need to remain very still to form properly. Once set up, I recommend making sure you have space set up away from everything to fit the number of cups you have.
More Valentine’s Day Science Experiments
For our complete collection of Valentine science experiments and activities, check here.
Printable Valentine STEM Project Pack
Countdown to Valentine’s Day with science and STEM! Pack includes complete instructions, templates, and images for 20+ activities. Bonus: printable science Valentine’s Day cards!