Growing Crystals From A Melt Worksheet printable pdf download

SALOL LAB

Name ___________________________

Growing Crystals From a Melt!

Period _______

Date ______________

In nature there are two basic processes used to form the crystals we all observe in

our everyday world. The simplest is to reproduce is the growth of crystals from a

solution. As the solvent evaporates, it leaves behind the solute (dissolved mineral

material) in solid crystalline form). You have probably seen the growth of crystals

from solution before and may have even grown some rock candy sugar crystals at

home. Today, you are going to perform a slightly more difficult crystal growth

experiment, growing crystals from a melt. You will actually take a solid crystalline

substance, melt it under very controlled conditions, and then allow it to cool and re-

crystallize under three different sets of conditions.

Problem: What is the relationship of crystal formation to cooling rate?

Materials: (Per lab group of 4 to 6 students)

3 Pyrex watch glasses

1 student hot plate with temperature control

1 sheet of clean wax paper

the top or bottom from a Petrie dish filled with ice cubes

crucible tongs

a watch with a second hand

1 magnifying hand lens per student

about one teaspoon of Salol (chemical name – Phenyl Salicylate)

Optional: Portable Digital Video Camera and tripod

Part 1: Rapid cooling.

1. Obtain all of your supplies from your instructor. Plug in the hot plate and set

it at 45 º C or 110º F. Do not turn the hot plate any higher or it will take too

long for your melt to cool and reform the crystals.

2. Tear the piece of wax paper into three parts and evenly divide your Salol

sample on the pieces. Place the Salol from one sheet in the center of one of

your clean watch glasses. Be careful to keep the solid in a nice central pile on

the watch glass. You want it to melt into one puddle. Do this for each of the

three watch glasses.

3. Place your Petrie dish of ice cubes off to one side of your work area. Set up

your camera and tripod to focus in on the area just on top of the ice cubes.

Use the largest zoom factor you can to see the most detail.

4. Place one of your watch glasses with the Salol on it just on the surface of the

hot plate. Do not push it in toward the center. You need to be able to

remove it with the tongs as soon as the solid melts completely. Watch the

glass and solid carefully, as soon as the material is completely melted start

your stop watch or clock.

Growing Crystals From A Melt Worksheet