Open the periodic table in the electronic application and calculate the relative molecular weight of some of the molecules you know.

Proof that particles of matter repel: liquids and solids are poorly compressible.
Proof that particles of matter attract: solids keep their shape.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.