Home Grown Crystal Experiment

Learn how to grow your own crystals at home with this fun hands-on experiment! There are many different kinds of crystals you can grow, and here I will show you how to grow blue copper sulfate crystals.

The recipe for this experiment comes from Graham’s How-to Guides. If you want to check out how to grow other kinds of crystals, check out this page here.

Grades: 3-5, 6-8

Background

How do crystals grow? Crystals have a particular molecular structure that gives them their unique shape in nature. The atoms, ions, or molecules in a crystal have a very ordered structure that forms in a lattice extending in all directions. Their molecular structures are also very geometric in patterns and shapes.

Image result for crystal structure

A crystal needs to have certain growing conditions in order to form in such a shape. The process in which crystals grow is called nucleation, when dissolved molecules in a solvent connect with one another and grow in size. The molecules will continue to attach to the surface of the growing crystal as it grows and expands. It will crystallize when it becomes large enough to fall out of the solution.

What You’ll Need

To grow your own blue copper sulfate crystals, you will need the following materials:

  1. copper sulfate
  2. distilled water
  3. jar
  4. fishing line
  5. Popsicle sticks

What to Do

Before you can begin to grow your crystal, you will need to create the saturated solution in which the crystal will grow. Graham’s How-to Guides created a great recipe that I am including here. To create your solution, follow these steps:

  1. Heat 100mL of distilled water in the microwave or on the stove. Be careful not to let the water boil
  2. Start with 25g of copper sulfate and stir it into the water. Continue to add more copper sulfate until no more dissolves.
  3. Pour the solution into a jar or other clear container
  4. Leave the solution to cool and watch as crystals grow over the next several hours

You can use the crystals that grow from this solution as seeds to grow even bigger crystals. Here’s how you can accomplish this:

  1. Take one of the crystals that has grown in your solution and tie some fishing string around it
  2.  Tie the other end of the line to a Popsicle stick or pencil to suspend the crystal inside of a jar with the solution
  3. Don’t allow the seed crystal to touch the sides of the jar
  4. Suspend the seed crystal in the jar containing the solution, making sure that the seed crystal is suspended in the solution
  5. Cover the top of the jar to prevent dust from coming in the jar
  6. Wait and watch your crystal grow

You can continue to add to the crystal to grow it even bigger. Here are some tips to make the biggest crystal possible:

  1. Remove the growing crystal and place to one side.
  2. Pour about 75% of the saturated solution into a clean jar #2.
  3. With the 25% remaining solution in beaker #1, re-dissolve the crystals on the bottom by microwaving on low power then stirring.
  4. Place beaker #1 containing not-quite-saturated hot solution in the freezer or ice water to cool it down, making it supersaturated.
  5. Add the supersaturated solution to jar #2, using a filter if necessary.
  6. Suspend the growing crystal in jar #2, place in fridge, and wait 8-12 hours.
  7. Repeat this process as desired to continue to grow the crystal even bigger

Here are some useful tips that the author of the recipe included:

  • Thin vs thick line: using 0.2mm nylon line prevents new crystals forming on the line. You can use a thicker line to grow a multi-crystal along the line directly without a seed crystal.
  • Solubility increases with temperature: careful not to add hot solution to the crystal beaker, as it may not be supersaturated and could dissolve your crystal. Wait for it to cool first.
  • Paint with clear nail polish: because CuS04.5H2O is a hydrated crystal, that dehydrates after a while to white powder (copper sulphate anhydrate). Painting helps reduce evaporation. Storing crystal on some copper sulphate powder can also help.

Connecting Concepts (NGSS)

There are a few ways you can incorporate this activity in your classroom. You can focus on the molecular and atomic structures as a part of a chemistry lesson, or you can focus on the geological aspects of it in a geology lesson. I have included the standards that I think can apply with this activity.

Develop models to describe the atomic composition of simple molecules and extended structures.

PS1.A: Structure and Properties of Matter

  • Substances are made from different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms.
  • Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals).
Construct an explanation based on evidence for how geoscience processes have changed Earth’s surface at varying time and spatial scales.

ESS2.A: Earth’s Materials and Systems

  • The planet’s systems interact over scales that range from microscopic to global in size, and they operate over fractions of a second to billions of years. These interactions have shaped Earth’s history and will determine its future.

ESS2.C: The Roles of Water in Earth’s Surface Processes

  • Water’s movements—both on the land and underground—cause weathering and erosion, which change the land’s surface features and create underground formations.
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