"مواد خالص" refers to pure substances that consist of only one type of particle. These materials have consistent properties and composition throughout. Examples include elements like هیدروژن and اکسیژن, as well as compounds like آب and نمک. In contrast to mixtures, which contain multiple substances, "مواد خالص" maintain their identity and characteristics under various conditions. They are essential in scientific research and industrial applications, as their predictable behavior allows for accurate measurements and reactions.