Why is it necessary to use models to study submicroscopic objects as atoms and molecules

Compared with the freezing-point depression of a 0.01 m c6h12o6 solution, the freezing-point depression of a 0.01 m nacl solution is

How many absorptions would you expect to observe in the 13c nmr spectra of the following molecules? a) 3-chloropentane b) cis-4-methyl-2-pentene

One similarity and one difference between an element and a mixture of elements