Growing Crystals-An Introductory Kit

Author(s): Jennifer Klipfel & Nabila Jahchan

Lab Kits - Teacher's Guide
SED 695B; Fall 2005

Overview: Grow your own collection of sparkling crystals.This lab is not for designed to delve into the chemical details of crystal growth. It is created and marketed to demonstrate the basic idea of crystals and how they are formed. It is a kit for younger elementary and junior high level that emulates the growth of real crystals in nature like diamonds and emeralds.

 

 
 

Topics addressed:

Kit visual

  1. Crystals are structures that are formed from a regular repeated pattern of connected atoms or molecules.
  2. Crystals grow by a process termed nucleation.
  3. During nucleation, the atoms or molecules that will crystallize
  4. Solutes are dissolved into their individual units in a solvent. The solute particles contact each other and connect with each other forming bigger crystals.
  5. Different salts grow create different size and shape crystals.

Standards Addressed:
Structure of Matter-Eighth Grade Standards
  1. Each of the more than 100 elements of matter has distinct properties and a distinct atomic structure. All forms of matter are composed of one or more of the elements. As a basis for understanding this concept:
    1. Students know the structure of the atom and know it is composed of protons, neutrons, and electrons.
    2. Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements.
    3. Students know atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers.
    4. Students know how to use the periodic table to identify elements in simple compounds.

    Investigation & Experimentation - Grades 9 to 12

    Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:

      1. Identify and communicate sources of unavoidable experimental error.
      2. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.
      3. Formulate explanations by using logic and evidence.
      4. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.

 

Procedure:

1-    Dissolve the crystal growing chemical in hot water

2-    Select a rock, and place it into the growing vessel.

3-    Add the solution, and let it cool down to room temperature.

4-    After just few hours the first crystals will stat to grow.

5-    Keep the vessel in an undisturbed place, so crystals will continue their growth for several days.

6-    Crystals can be removed from the solution after about one week.

 

 

 

Questions:

1-    Why hot water should be used to dissolve the salt?

In order to grow a crystal, you need to make a solution which maximizes the chances for the solute particles to come together and form a nucleus, which will grow into your crystal. This mean you will want a concentrated solution with as much solute as you can dissolve(saturated solution) and more solute dissolve in hot water than in cold water.

2-    Why a rough rock has to be used to grow the crystals on?

Sometimes nucleation can occur simply through the interactions between the solute particles in the solution(called unassisted nucleation), but sometimes itŐs better to provide a sort of meeting place for solute particles to aggregate (assisted nucleation). A rough surface tends to be more attractive for nucleation than a smooth surface.

3-    How can you keep your treasure crystals?

Crystals that were made from a water(aqueous) solution will dissolve somewhat in humid air. Keep your crystal beautiful by storing it in a dry, closed container. You may wish to wrap it in a paper to keep it dry and prevent dust from accumulating on it.

4. How does this simple crystal-formation lab relate to naturally occuring crystal formation we can experience in our world?
Many formations found in nature are created from the slow evaporation of water from a highly concentrated solution of different salts, or the precipitation of solids like limestone out of solution as in the case of the Tufa formations in Mono Lake.. Below, click on the links provided to see two formations that will amaze you and allow you to see some real application of this principle in the natural world.

This first link is to pictures and explanation of Tufa Formations in Mono Lake. These are limestone towers that form underwater and are visible as the water level in Mono Lake falls.
http://www.monolake.org/naturalhistory/tufa.htm

This second set of links are of the Tonto Natural Bridge near Payson, Arizona. It is considered to be the largest travertine bridge in the world. A partial part of the story of its formation has to do with precipitation and crystalization out of a solution.

http://users.sisna.com/archman/TontoNaturalBridge.html
http://skywalker.cochise.edu/wellerr/students/tonto/T0NTO.htm


Initial set up to grow the crystals

"Emerald" crystals, ammonium phosphate

"Rose-quartz", ammonium phosphate

"Aquamarine" crystal, monoammonium phosphate

"Diamond" Crystals, potassium aluminum sulfate

"ruby" crystals

potassium aluminum sulfate

 

 

References & Links:

The link below offers some troubleshooting advice for crystal growers and directions for growing different crystals
http://www.chemistry.co.nz/crystal_recipes.htm

This lab from Carolina Supply is a low-cost simple introductory crystal growing lab.
http://www.carolina.com/calendar_activities/2002/0203.asp

The link below is a great introductory crystal lab for 6-8 grade.
http://www.the-aps.org/education/k12curric/activities/pdfs/hills.pdf