hellppp with explaniation please!!!!

A crystalline compound melts at 1119 - 112C and the melting point capillary is set aside to cool. Repeating the melting Point analysis with the same capillary reveals a much higher melting point of 140C. Yet repeated recrystallization of the original sample yields sharp melting point no higher than 114C. Explain the behavior of the sample that was cooled then remelted. / A compound melts at 120 - 122C on one apparatus and 1289 - 129C on another. Neither apparatus is temperature calibrated. Propose an experiment you could use to confirm the identity of your sample without the need for calibrating the apparatus. Another student reports a melting range of 136-138C for the compound in question 1 (above). The student mentions takes note that the rate of heating was about 12C per minute. NMR spectroscopy analysis of this student's product does not reveal impurities. Explain the low Melting Point range