A student performs two melting-point determinations on a crystalline product. In one determination, the capillary tube contains a sample about 12 mm in height and the melting range is found to be 141\deg 142\deg C. In the other determination, the sample height is 45 mm and the melting range is found to be 141\deg 145\deg C. Explain the broader melting-point range observed for the second sample. The reported melt- ing point for the compound is 143\deg C.2. Another student reports a melting range of 136\deg 138\deg C for the compound in Question 1 and mentions in her notebook that the rate of heating was about 12\deg per minute. NMR analysis of this students product does not reveal any impurities. Explain the low melting point.