Arrange in increasing order of acidic strength: methanol, ethanol, water, phenol.

Approximate pKₐ values: phenol ≈ 10, water ≈ 15.7, methanol ≈ 15.5, ethanol ≈ 15.9. Lower pKₐ ⇒ stronger acid. Ordering ascending acidity: **ethanol < methanol < water < phenol**. **Why:** phenol's conjugate base (phenoxide) is stabilised by resonance into the aromatic ring, dramatically lowering its pKₐ versus aliphatic alcohols. Among the alcohols, the +I effect of larger alkyl groups *destabilises* the alkoxide (donates electron density) so ethanol is weaker than methanol.