Mechanism: Nucleophilic Substitution
Electronegativity is the ability of an atom to attract a bonding pair of electrons. As bromine is more electronegative than carbon, the C-Br bond is polar, meaning the electron density in the covalent bond is attracted towards the bromine. Therefore Br is left with a partial negative charge, and the attached C now has a partial positive charge. This means the partially charged C is susceptible to nucleophilic attack.
A nucleophile is an electron pair donor, so the NaOH dissociates to form Na+ and -OH, with -OH acting as the nucleophile. The lone pair of electrons on the O atom is donated to the partially positive C, forming a bond between C and OH. However, C can only have 4 covalently bonded atoms so the C-Br bond breaks, with Br- as the leaving group. Therefore, ethanol is produced.
Drawing to be shown in interview.