Phenol and formaldehyde undergo condensation to give a polymer $(A)$ which on heating with formaldehyde gives a thermosetting polymer $(B)$. Name the polymers. Write the reactions involved in the formation of $(A)$. What is the structural difference between the two polymers?

(N/A) Phenol and formaldehyde undergo condensation to give a polymer $Novolac$ $(A)$,which on heating with formaldehyde gives $Bakelite$ $(B)$ as a thermosetting polymer.
$Novolac$ is a linear polymer,while $Bakelite$ is a cross-linked polymer.
The reactions involved in the formation of $Novolac$ are:
$1$. Phenol reacts with formaldehyde in the presence of an acid or base catalyst to form $o$-hydroxybenzyl alcohol and $p$-hydroxybenzyl alcohol derivatives.
$2$. These derivatives undergo condensation polymerization to form the linear polymer $Novolac$.