$(a)$ Give chemical tests to detect the presence of:
$(i)$ Ethanol
$(ii)$ Ethanoic acid
$(b)$ Why is ethanoic acid called glacial acetic acid?

(N/A) $(i)$ Ethanol test (Reaction with Sodium metal):
Ethanol reacts with sodium metal to evolve hydrogen gas,which can be tested by bringing a burning splinter near the gas,producing a 'pop' sound.
$2 CH_3CH_2OH + 2 Na \rightarrow 2 CH_3CH_2ONa + H_2 \uparrow$
$(ii)$ Ethanoic acid test (Esterification reaction):
Ethanoic acid reacts with ethanol in the presence of an acid catalyst to form an ester,which has a sweet,fruity smell.
$CH_3COOH + CH_3CH_2OH \xrightarrow{H^+} CH_3COOCH_2CH_3 + H_2O$
$(b)$ Pure ethanoic acid has a melting point of $290 \, K$. In cold climates,it often freezes into an ice-like solid during winter,which is why it is known as glacial acetic acid.