When determining the melting point of a solid, the purer the material, the melting point is _____ and __________.

When determining the melting point of a solid, pure substances typically exhibit a melting point that is both narrower and closer to the literature value. This phenomenon occurs because impurities disrupt the orderly lattice structure of a crystalline solid, leading to a broader melting point range. In contrast, pure substances have a well-defined melting point where the transition from solid to liquid occurs sharply due to their consistent molecular or ionic structure.

As substances approach their melting point, the energy input is uniformly used to overcome intermolecular forces in pure solids, resulting in a precise melting temperature. Therefore, when evaluating the melting point of a sample, a narrow range signifies high purity, and when it closely aligns with the established literature value, it confirms that the sample is not only pure but also representative of the expected behavior of that compound under ideal conditions. This characteristic is a key indicator in organic chemistry for assessing the purity and identity of a material.