There is actually a few differences. Firstly, a pure substance can be an element or compound. A compound is a subtance where the elements made up of it are bonded by chemical bonds, either ionic or covalent bond. A mixture may consist of a combination of elements or compound, where there is no forces of attraction between them. Pure substance: Carbon dioxide, water, sodium chloride. Mixture: Alloy like brass (zinc & copper), chalky water (calcium carbonate and water). Pure substance has fixed melting and boiling point whereas mixture has a range of melting and boiling point due to presence of impurities. Pure substance has fixed composition by mass but mixture has varying degree of composition. Pure substance cannot be separated into other substance by physical means like distillation, filtration unlike a mixture. Pure substance has to be separated by chemical means like electrolysis to it\'s constituent parts. Solution There is actually a few differences. Firstly, a pure substance can be an element or compound. A compound is a subtance where the elements made up of it are bonded by chemical bonds, either ionic or covalent bond. A mixture may consist of a combination of elements or compound, where there is no forces of attraction between them. Pure substance: Carbon dioxide, water, sodium chloride. Mixture: Alloy like brass (zinc & copper), chalky water (calcium carbonate and water). Pure substance has fixed melting and boiling point whereas mixture has a range of melting and boiling point due to presence of impurities. Pure substance has fixed composition by mass but mixture has varying degree of composition. Pure substance cannot be separated into other substance by physical means like distillation, filtration unlike a mixture. Pure substance has to be separated by chemical means like electrolysis to it\'s constituent parts..