Step-by-step explanation:
Determination should be slow (temp rise should not exceed 1C) so that sufficient time may be used to pass thermometer from the heating block equivalent to the sample. If you proceed too quickly, the temperature of the sample differs much from that at the thermometer and the sample seems to have a broad range. Before the thermometer the temperature reaches the sample and the temperature observation is less than predicted.
Remember that an accurate measurement requires a modest heating rate at the melting point. List the thermometer's temperature when the sample begins to melt and again record the temperature when every sample has melt (this gives you the melting point range)