Vapour pressure and boiling
Liquid State · Chemistry
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Water boils at 100°C in Delhi but ~95°C in Shimla. Explain. Step 1: Boiling starts when vapour pressure equals external (atmospheric) pressure. Step 2: Shimla's altitude → lower atmospheric pressure (~0.85 atm). Step 3: Water's vapour pressure reaches 0.85 atm at ~95°C — before 100°C. Step 4: So it boils 'early'. Pressure cookers reverse this: higher P → bp ~121°C, faster cooking. Boiling point is not a fixed property — it depends on external pressure.