Want to learn how to how to grow salt crystals overnight using easy to find materials? Of course you do!
Any exploration of science for kids is not complete without growing some crystals….am I right? In fact, at the science fair this past year crystal growing projects were the project de jour, and I can understand why, growing a Crystal Garden has ranked pretty high up there on my list of fun science experiments since I myself was a kid!
Now one of the big drawbacks to many crystal growing projects is the time involved. I’ll be honest, I am not a patient woman and though I proselytize patience to my kids, I’m not a very good example of this virtue! So days of waiting for a crystal garden to grow pretty much sent this idea to the “someday” list. That is until I discovered Epsom salt crystals….leave them overnight and wake up to magic! Oh how much do I love thee Epsom Salt!
Before we get started let me clarify, growing crystals using Epsom salt will not yield giant geodes bursting with color; Epsom salt crystals are small, delicate, and slivery. Instead of one or two mega crystals this science experiment for kids will give you hundreds of miniature crystals; they look a little bit like shards of glass and if you’re lucky you may get a few that look like snowflakes…
Also plan on making 3-4 crystal gardens. The crystals grow differently, some were delicate and lacy, other were more rocky and gem like. Be sure to make a bunch to delight you and the kids!
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- Epsom Salt
- Clean Glass jars Buy in bulk here
- Food Coloring (optional)
- Hot Tap Water
- Bowl or glass measuring cup
- Pebble or sand
- Microwave (optional)
- Step One | Measure You will be using a ratio of 1:1 water to Epsom Salt for this project. Add 1 cup of Epsom salt to your jar/votive. If you are working with larger jars feel free to add more salt but be sure to make a note of how much so you can add the same amount of water.
- Step Two | Heat the Water Add 1 cup of water to a microwave safe bowl. Heat the water in the microwave for 45 seconds. Alternatively use very hot tap water and skip the microwave.
- Step Three | Add Color If you are using color, add a dash of food coloring to the water. Stir.
- Step Four | Combine Pour the water into the jar with the salt. Stir the salt and water for 1-2 minutes to dissolve the salt. Don’t worry if some of the salt remains undissolved at the bottom of the jar.
- Step Five | Cool Drop in a pebble or a few grains of sand. Crystals need something to grow on and one little impurity in the water like grain of sand will should help ensure they have a place to nucleate.
- Step Six | Cool Place the jar in the back of your refrigerator. Alternatively, quick cool the mixture for 10 minutes in the freezer and then move it to the refrigerator. Cooling in the freezer first yielded crystal growth in 90% of our experiments. We had just a slightly lower success rate going straight from mixing to the fridge.
- Step Seven | Let ’em Grow Leave the mixture overnight in the fridge. Crystals may start forming in as little as 3 hours but we got the best results when we made the gardens in the evening and left them to sit undisturbed overnight Bonus: My daughter was excited to wake up and see how they had grown!
- Step Eight | The Reveal Carefully pour out the extra liquid. It’s okay to leave a little liquid at the bottom of the jar. If you colored your water it will be hard to see if any crystals have grown until the excess liquid is removed. Clear water is easy to check.
- Step Nine | Clean Use a wet paper towel to gently wipe away excess salt and color that may be on the upper portion of the jar. This will help you see the lovely crystal garden through the glass. Be careful not to damage any of your crystals!
You’re done! Hand the kids a magnifying glass for additional exploration. My kids really wanted to touch the crystals. That’s okay but let them know they are delicate and break easily.
Tips & Troubleshooting
Science for kids is not without trial and error! Here are some tips I learned after repeating this experiment over 20 times…
- Don’t overheat the water! I know it’s tempting to really heat that water up to make the salt dissolve, but all the experiments we did with really hot water, heated more than 45 seconds in the microwave, failed miserably.
- Stir for at least one to two minutes! This is tough one for littler kids. My daughter was done stirring within a few seconds but you really need to get that water super saturated with salt to make the crystals grow. The less dissolved the salt is the smaller the crystals will be and worst case they may not grow at all.
- Let them grow even longer in the fridge. Leave them in the fridge longer than overnight and they should continue to grow. I left a few in the fridge for a over a week and the results got even better!
- DO NOT let them sit in water at room temperature. Any crystals that have formed will deteriorate in the water at room temp. Once the crystals have formed and you want to preserve them you will need to pour out the water. I had some gorgeous crystals form in the fridge over the course of a week or so and I took them out and left them on the counter in the water. I came back the next morning to find they had flattened out. The one garden I poured the water out of remained stunning.
- Make a Crystal Suncatcher with the leftover water!
Let’s Talk Science
Here are a few terms we need to know to understand the chemistry involved in learning how to grow salt crystals:
- Crystals Crystals are a type of material that is formed by patterns of repeating molecules. To the naked eye they have flat surfaces and facets. Crystals form when a liquid cools very slowly and/or when water evaporates from a chemical mixture leaving behind the solute (see below) whose molecules re-form into new geometric shapes i.e. crystals
- Solute A substance dissolves in another substance.
- Saturation When a mineral like salt (the solute in this project) is dissolved in water, the water can only hold certain amount of the solute. A liquid is saturated when the maximum amount of solute is dissolved in it. Hot liquids can hold more solute than cold liquids.
- Nucleation & seed crystals When an impurity is introduced into a saturated solution the solute will begin to recrystallize around that impurity. This is the site of nucleation. Often a large crystal is used to grow smaller crystals, this is a seed crystal. In our experiment the sand and pebbles are acting as the seed crystal.
What is happening in this project:
In our overnights crystals we first mix up a super saturated batch of salt water. As the mixture both cools in the refrigerator and the water begins to evaporate, the atoms in the salt start reforming around the pebbles and/or sand particles causing the salt crystals to reform in new geometric formations.
How to turn this in a Science Fair Project
Let’s turn this topic into an experiment! Here’s how you can take this to the science fair:
- Ask yourself questions Some question ideas: What are the best materials for nucleation? What is the ideal temperature for crystal growth- you can explore the water temperature or the temperature in the refrigerator. What is the ideal salt/water ratio for crystal growth?
- Research Do research online and at the library to try and predict the answer to your question. For instance, research seed crystals, saturation, and the best methods for growing crystals.
- Make a hypothesis A hypothesis is your prediction of the answer to your question based on your research. It may or may not be true.
- Experiment! Test you your hypothesis by testing the variables and documenting them. Be sure to take notes of each experiment and what happens; this is called your data.
Experiment with nucleation materials Try crowing crystals using sand, rocks, dust, glitter, etc. as your seed crystal. Does that change the way the crystals form? Does the size of the object make a difference in the way the crystals form?
Test different temperatures Try using different water temperatures to grow crystals. Does that change the way they grow? Try cooling the crystals at different temperatures, i.e. in the freezer, refrigerator, room temperature, and observe what happens.
Find the best salt/water ratio for crystal growth We used a 1:1 ratio in this experiment but what happens if you vary that ratio? Experiment and document the results.
- Draw conclusions Based on your experiments form a conclusion. Was your hypothesis correct?
- Share your findings Create a presentation with your findings. Include your research, hypothese, the data you collected and your conclusions. Be sure to include images and samples
See more Science Fair Project ideas here
Now that you know how to grow salt crystals, here’s a little something you can try with the leftover saturated water: Make Crystal Suncatchers:
learning how to make crystals from epsom salt is really simple and a great idea for a science fair project!
For more fun science experiment ideas for kids hop over here
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