All pure substances contain ____ particles or group of particles having a definite set of property​

Answer:

A pure substance contains only one type of particles which can either be atoms or molecules or elements or compounds.

A pure substance cannot be separated into other kinds of matter by any physical process but a mixture can as they are impure substances because they contain more than one particles. Ex: salt solutions.

A pure substance has fixed composition as well as fixed melting and boiling points. Ex: salt.

Pure substances cannot be exemplified by all elements other than nickel because pure nickel is an element containing only one kind of particles.