Why are homologous series of carbon compounds so called? Write the chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their $(i)$ physical properties,and (ii) chemical properties.

(N/A) homologous series is a group of organic compounds having the same functional group and similar chemical properties,in which all successive members differ by a $-CH_2$ unit.
Two consecutive members of the homologous series of alcohols are:
$(i)$ Methanol: $CH_3OH$
(ii) Ethanol: $C_2H_5OH$
$(i)$ The physical properties (such as melting point,boiling point,and solubility) of the compounds in a homologous series are determined by the length of the carbon chain (molecular mass).
(ii) The chemical properties of the compounds in a homologous series are determined by the functional group present in the molecule.