Igneous rocks often have crystals. But why are some crystals small, while others are large? It all comes down to cooling rate. In this lab, students will examine the relationship between cooling rate and crystal size.

Part 1: Students will look at epsom salt crystals under the microscope. They will compare crystals that formed rapidly to crystals that formed slowly.

Materials needed: epsom salt, water, dye, hot plate, glass slides, microscopes, beaker, and eyedropper.

Part 2: Students will look at salol (phenyl salicylate) crystals as they form under the microscope. Students will compare crystals on a warm slide to crystals on a cold slide.

Materials needed: Phenyl salicylate, hot plate or water bath, microscopes, glass slides, eyedropper, fridge or ice bath.

Included in your purchase:

- 2 page student lab worksheet (editable)

- 9 slide powerpoint to accompany the lab (editable)

- Teacher set-up directions, troubleshooting tips, and answer key