there are a lot of mystery white powder labs out there on the internet, but this is the one that is the best. it has been done by 100's of my students over the years.
there are six white powders given to the students. the conduct a series of experiments with water, acid, iodine and indicator to get results. then a 7th mystery powder is given and based on the students experimenting, they have to determine which of the six powders they have been given. i usually give them starch.
Physical and Chemical Changes Experiment
Formula of a Hydrate Experiment
Double Displacement Experiment
The absolute two best products I have for sale that every science teacher needs are the games:
The Periodic Table Challenge Game
[good for all grades]
The Periodic Table of Rappers Game
[good for chemistry classes]