pure substances have a sharp melting point, if the substance is impure, that is a mixture of substances then each one will have its own melting point. Each will melt separately. If the mixtures of substances interact with each other in some way then the melting point will be over a range and not a sharp point.
You could compare the known mp of your substance with that in a data book and compare them
pure substances have a sharp melting point, if the substance is impure, that is a mixture of substances then each one will have its own melting point. Each will melt separately. If the mixtures of substances interact with each other in some way then the melting point will be over a range and not a sharp point.
You could compare the known mp of your substance with that in a data book and compare them