Dimethyl ether and ethyl alcohol are

Which of the following organic structures is $NOT$ an isomer of the compound $CH_3COCH_2CH_2CH_2CH_3$?

An isomer of ethanol is

Explain the following terms:
$(a)$ Isomerism
$(b)$ Position isomerism
$(c)$ Chain isomerism
$(d)$ Functional group isomerism
$(e)$ Metamerism
$(f)$ Optical isomerism

Identify the pairs of compounds that represent position isomerism.
$(I)$ $CH_3-CH_2-CH_2-CH_2-OH$
$(II)$ $CH_3-CH_2-CH(OH)-CH_3$
$(III)$ $CH_3-C(OH)(CH_3)-CH_3$
$(IV)$ $CH_3-CH(CH_3)-CH_2-OH$
$(V)$ $CH_3-CH_2-O-CH_2-CH_3$
$(VI)$ $CH_3-O-CH_2-CH_2-CH_3$
$(VII)$ $CH_3-O-CH(CH_3)-CH_3$

Match the column $I$ with column $II$.

Column $I$ (Compounds)	Column $II$ (Relation)
$(i)$ $CH_3-CH_2-C(CH_3)_2-Cl$ and $(CH_3)_3C-Cl$	$(P)$ Homologues
$(ii)$ $C_6H_5-O-CH_2-CH_3$ and $C_6H_5-O(CH_3)-CH_3$ (ortho-methylanisole)	$(Q)$ Functional group isomers
$(iii)$ $C_6H_5-O-CH_3$ and $2-methylphenol$	$(R)$ Metamers
$(iv)$ $CH_3-CH(CH_3)-CH_2-OH$ and $(CH_3)_3C-OH$	$(S)$ Position isomers