Neeraj says water always boils at exactly 100°C, wherever you are — on the plains, on a mountain…

Why

Neeraj has learned a genuinely reliable fact — at sea level, water really does boil at exactly 100°C, every single time, and that number is worth trusting there. What he's missed is that this number quietly assumes normal sea-level air pressure, without saying so. Water boils when it has enough energy to push its way out against the air pressing down on it, and up on a mountain there is LESS air above pushing down, so water needs less energy — and so a lower temperature — to break free and boil. On a high mountain, water can boil at 90°C or even lower, well before it feels properly hot, which is exactly why rice and dal take longer to cook at high altitude — the water is boiling, but not hot enough to cook food quickly. Test: this is why mountaineers carry pressure cookers even for simple meals at altitude, to force the boiling point back up. His sister is right: 100°C is the boiling point only at sea-level pressure, and it genuinely changes with altitude.