What are the simplest tests that are used for identification of purity of the chemical sample?

PLACEHOLDER ANSWER - the answer is a description of tests. A pure solid has a sharp, fixed melting point, and a pure liquid has a constant, fixed boiling point at a given pressure. Impurities lower and broaden the melting range and change the boiling point. So measuring the melting point or boiling point is the simplest test of purity.