Try segregating the things around you as pure substances and mixtures.

Pure substances:Water, salt, iron and sugar.

Pure substances are substances that are made up of only one kind of particles and has a fixed or constant structure.

Mixtures:Wood, milk, air, soil and steel.

A mixture is a material made up of two or more different substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are retained