Crystallography

Crystallography:

A LESSON PLAN ON THE GEOLOGY EXPERIMENT CARRIED OUT BY SPANISH STUDENTS OF ESCUELA PROFESIONAL LA SALLE, PATERNA (VALENCIA)
  1. PURPOSES
  • Get students started in geology through crystals
  • Get a closer look at different types of crystals
  • Learn the fundamental concepts and notions of internal and external crystallography.
  1. OBJECTIVES
  • Understand the concept of a crystal and its relationship to minerals
  • Understand the structure of crystals
  • Understand that crystallography is a science
  1. CONTENTS
  • Introduction to crystallography

Crystallography is the science that studies crystals. Crystals are formed from a solution when the solvent evaporates.

The study of crystalline solids allows us to understand that matter is composed of atoms. A crystal has a structure called a unit cell.

We find crystalline solids in nature, such as minerals and rocks. We also find them in metals, such as steel or aluminum, in this way we can relate it to chemistry.

The size and perfection of the crystals depends on the conditions in which they have been formed. Slow cooling causes the crystals to grow little by little to ensure that the crystal is more perfect, while rapid cooling results in small and imperfect crystals.

  • Difference between mineral and crystal.

Crystal: Homogeneous solid crystal with a defined chemical composition and an ordered internal structure.

Mineral: Homogeneous, natural and inorganic solid mineral, with a defined chemical composition and ordered internal structure. A mineral can be formed by small crystals or thick and long. If it does not have crystals, it is amorphous.

  • Saturated solution

In a saturated solution, the maximum amount of solute is dissolved in a volume of solvent. Solutes and solvents are the components of a solution. A solute is the substance that dissolves in the solvent.

  1. ACTIVITIES
  • Preform the solubility curve

Performing a solubility curve, consists of gradually heating the solute in the solvent and then allowing it to cool.

  • Crystal formation (nucleation)

Growth of very small solid bodies in a supersaturated fluid phase.

  • Crystal growth

Incorporation of new molecules into the already formed and stable nucleus.

EXAMPLES

It is not easy to recognize the crystals around us. Let’s look for some examples:

  • Analgesic aspirin: formed by tiny crystals which format it.
  • In the human body: bones and teeth have a crystalline structure. Both are made up of hydroxyapatite crystals.
  • In food we can distinguish several cases:
    • Salt is a crystal in which the chlorine and sodium atoms form a cubic lattice,
    • Sugar also has crystalline forms,
    • Chocolate, since cocoa butter crystallizes in different ways.
  • Crystallography techniques which have revealed the structure of different materials such as lysosomes, ribosomes, viruses and DNA.