Crystal Growth Activity

Objective

Students will observe the effect of temperature on rates of crystal formation and crystal size.

Background

Phenyl salicylate (C13H10O3), also known as salol, was formerly used as a sunscreen and antiseptic. Now used as a plasticizer and in some medical preparations. Avoid contact with skin - may cause contact dermatitis in sensitive individuals.

References: Fisher Scientific MSDSexternal arrow

Materials

Procedure

  1. Observe all safety procedures! Wear your goggles.
  2. Melt salol in a water bath (melting point = 107°F). Do not over heat !
  3. Place the glass stirring rod in the melting salol so that it is the same temperature as the salol.
  4. Place some microscope slides on ice so that they are quite cool. Keep the slides dry.
  5. Place some slides on a hotplate turned to its very lowest setting.
  6. Place a drop of salol in the center of a cool slide.
  7. Observe the slide under the microscope.
  8. A seed crystal may need to be placed in the drop of salol. It can several minutes for crystallization to complete.
  9. Place a drop of salol in the center of a warm slide.
  10. Observe the slide under the microscope.
  11. Record your observations.
  12. Places slides in the waste beaker provided by your instructor.
  13. Wash your hands.

Examples of Crystal Growth

Analysis

  1. Describe the size of the cool slide and warm slide crystals.
  2. Describe the rate of crystal formation of the cool slide and warm slide.
  3. What evidence do you have that the liquid salol was initially in a super-cooled condition?
  4. Relate this activity to igneous rock formation.