Materials: hot water (either bring hot water into the classroom, or bring in a pot and charcoal stove and make it before class), smooth cold surface (like glass or acrylic) or string, salt (either epsom salt, copper sulfate, or alum-- see above for preparation)
Procedure:
Dissolve a lot of salt in the hot water to form a super-saturated solution. Stir to make sure that all of the salt has dissolved before adding more. Keep adding salt until the hot water is saturated and the salt no longer dissolves. Then, pour a bit of the salt solution onto the cold surface to watch the crystals form. When the water cools down, it can no longer hold as much salt. If you like, you can use a piece of string instead of glass to cause the crystals to form. Put the string into the hot solution for a few seconds, then pull it out and show students the salt crystals. As soon as the dissolved salt finds a rough surface, the crystals will form.

Sublimation
Materials: iodine crystals (see preparation), 500ml Voltic bottle, warm water bath
Preparation:
To create solid iodine, react iodine tincture from the pharmacy with battery water and
bleach. Do this outside to not breath the toxic chlorine gas! Filter and wash the crystals, then
bring the product to class in a sealed bottle so they do not sublimate upon heating.
Procedure:
please edit this as needed
Place your iodine crystals in a clear, sealed bottle. Heat up the bottle using a warm water bath, and note the purple iodine gas as the crystals sublimate.