Heating blue crystals
Hydrates become dehydrates
Striking color change
This lab happens to be one where the procedure and materials are different for AP vs General Chemistry, but it gets good results both ways. The haiku above specifically refers to the general chemistry version of the lab where blue copper (II) sulfate is dehydrated into its white crystalline form.
As a side note, I feel really bad about leaving out my original middle line "Color changing chemistry" because I love the alliteration and the match with "crystals" in the first line, but alas I could not get anything to work with it and so I changed tack.