mrteverett

I would add that it is probably difficult to avoid some sort of post-reaction to occur. In many cases, a decomp (or similar reaction) may be carried out in an environment (e.g. nitrogen) that is inert towards the target metal. However, magnesium makes the nitride and oxide when heated in air, so it may be difficult in practice to get pure Mg this way. Electrolysis of the molten compound is a better bet I suppose.

If you wanted to perform a simple pH identification lab - use red cabbage indicator. Break off some pieces and boil in water (preferably distilled) until the color leaches out. Let it cool, and use a dropper to test common household objects. You may wish to soak white paper in the cabbage juice and allow it to dry - creating an indicator paper that could be used to test other substances.