A student obtained a solid product in laboratory synthesis. To verify the identity of the solid, she measured the milting point and found that the material melted over a 12°C range. After it had cooled, she measured the melting point of the same sample again and found that this time the solid HUD a sharp melting point at the temperature that is characteristic of the desired product Why were the two melting points different? What was responsible for the change in the melting point?