Q.The alcohol used in thermometers is _______.

Alcohols are polar and hydrogen-bond strongly to each other and to water, giving lower alcohols (up to about 3 carbons) appreciable water solubility and boiling points that rise with molecular mass but FALL with increased chain branching (weaker van der Waals contact between more compact, branched molecules). Alcohols are neutral in water (no reaction with NaHCO3 or NaOH) but react with active metals like Na or K to liberate H2 gas (a positive alcohol test), since their alkoxide conjugate base is destabilised, not stabilised, by the electron-donating +I effect of the alkyl group. The Lucas test (conc. HCl + ZnCl2) distinguishes primary/secondary/tertiary alcohols by how fast the clear reagent turns turbid as the water-insoluble alkyl chloride forms (tertiary fastest, primary only on heating). Reactions at the C-O bond include: formation of alkyl halides with HX (reactivity HI>HBr>HCl, tertiary>secondary>prim …