Growing Salt Crystals at Home with just salt (Sodium Chloride) and water is a super fun activity for kids.
We have previously tried some crystal ornaments for Christmas (hearts, snowflakes, candy canes & Snow Man) using Borax.
Unlike Borax, Salt crystal takes few days or up to a week to grow/form. But growing salt crystals is a great way to teach the science behind the salt making.
Growing Salt Crystals at Home
Things We Need
Table Salt (Sodium Chrolide – NaCl)
Color Papers cut into different shapes (optional)
Food Colors (optional)
Process of Making Salt Crystals
Fill your container halfway with warm water. Warm water helps to dissolve the salt quickly.
Add a cup of salt to the warm water and stir it continuously until the salt is completely dissolved. Repeat the process until you cannot get any more salt to dissolve. The final salt solution should not have any residue of salt. This is called a supersaturated salt solution.
Now gently pour the saltwater onto different plates. You may choose to add few drops of food color in your solution to make colored salt crystals.
Place the cut papers. Since we targeted to create crystals to make Christmas ornaments – we made a Christmas tree, star, and snowman. But this is completely an optional step. You can even form crystals just on the plate without any papers.
Now we need to place the plates in sunlight. The entire process of salt crystal formation will take about 3 to 4 days, depending upon the room temperature and availability of sunlight.
Here is our observation for the next consecutive days.
The paper is still wet buried in the saturated salt solution. We started seeing a layer of salt crystal that formed on the top of the solution.
The salt crystal layer was thickened, and we could see salt crystals evidently on top of the paper and floating later on top of the saturated solution.
Almost all the water from the saturated solution evaporated, leaving behind the crystallized salt. The layer was thick enough to show the crystals formed on top of the immersed paper.
The paper pieces were still wet. So we had to take them out from the plate to dry off completely in sunlight.
You can see Salt crystals formed all over the paper, including the backside. Now the Christmas tree-cutting had a full snowy effect due to salt crystal formation
Science Behind Growing Salt Crystals
Here are some important terms that you need to know before understanding the science behind salt crystals.
Solution: When you mix two or three substances evenly or completely to create a homogenous mixture, that is called a solution.
Solvent: Substance that dissolves the other one (In our experiment – Water is the solvent).
Solute: Substance that gets dissolved (In our experiment – table salt)
To make a solution, one must dissolve a solute in the solvent. When you put the solute in the solvent, the molecules of those substances run into each other to create the dissolving process. Since these molecules are in constant motion – the solvent molecules bombard with solute molecules.
The dissolving process usually takes more time. To reduce the time taken to form the solution – you have two options:
Increase the temperature of the solution.
Try to increase motion between the molecules by stirring the solute and solvent together.
Once the solute is dissolved in solvent – that produces three types of solution:
Unsaturated Solution: The solution which can absorb more solute.
Saturated Solution: Where you can no longer get the solute dissolved anymore.
Super Saturated Solution: It represents a solution that can absorb more solute than in a normal scenario. For example – Warm water can absorb more salt than water at room temperature.
So, let us understand how the Crystallization Process happened to form Salt Crystals:
Once the solute (salt) is dissolved in the solvent (water) – the ionic bonds disassociate themselves to form ions as these ions will then be attracted by the molecules in the solvent (water).
When the solution is let to cool down, the molecules in solvent (water) start bonding together, leaving the ions from salt out of place. These left-out ions create sediment in the paper as well as on the plate. As the water evaporates, the niacin and chlorine atoms bond together as there is no water molecules to separate them. As time passes, more of these fallen molecules of salt bond together to form salt crystals (in cube shapes).
We have made this a Christmas-themed science project. You can choose your favorite theme. E.g., Try making egg-shaped crystals for easter.
For example, try using different salts – repeat the experiment with sea salt, un-iodized salt, Epsom salt, borax salt, and iodized salt. Check the different shapes of crystals formed.
Change the solvent – instead of tap water, try it with distilled water and observe changes in crystal shapes.