Different substances may differ from each other.
1) The composition of the molecules.
Example – carbon dioxide CO2 and ammonia NH3
2) The structure of molecules having the same composition.
An example is isomers of organic substances, for example n-butane (CH3-CH2-CH2-CH3) and isobutane (CH3-CH (CH3) -CH3).
3) The structure of the crystal lattice.
An example is carbon and diamond.
The volumes of molecules of different substances do not coincide and depend on the number and type of atoms included in the molecule – from monatomic molecules of inert gases to huge polymer molecules of organic substances.
The compositions of molecules of different substances in some cases may coincide (example 2), but in this case they will have a different structure.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.