Ammonium Nitrate: Hi. Wondering if anyone uses ammonium nitrate for senior chemistry? Have a teacher who has requested some ammonium nitrate for making rockets?

Ammonium Nitrate: Hi. Wondering if anyone uses ammonium nitrate for senior chemistry? Have a teacher who has requested some ammonium nitrate for making rockets?
Chemicals (cold pack practical): I would like use the following chemicals for a cold pack prac: ammonium chloride, ammonium nitrate, magnesium sulfate and sodium thiosulfate.
Ammonium nitrate: Hi, Has anyone else had any trouble with ammonium nitrate absorbing water? Mine has become a clear mixture of liquid and crystals.