Friction from a car's brakes causing it to stop is it a contact force?

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

Answer ozone (o3) is made of three atoms of oxygen, it is a molecule;