What is the effect of the following on the observed melting point of the compound:

1.What is the effect of the following on the observed melting point of the compound: a) insoluble purity, such as charcoal; b) incomplete drying of the sample; c) less recrystallization solvent was used than it was needed?2. Three test tubes, labeled X,Y, and Z, contain substances with approximately the same melting point. How could you prove that the three compounds are different?