Assertion (A): The boiling point of water decreases as the altitude increases. Reason (R): The atmospheric pressure increases with altitude. Codes:

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Correct answer: A is true but R is false. The boiling point of a substance is the temperature at which its vapour pressure equals the external atmospheric pressure, causing it to change from a liquid to a gas. Assertion (A) is true: The boiling point of water decreases with increasing altitude because atmospheric pressure decreases at higher altitudes. At lower pressure the water molecules require less energy to escape into the vapor phase, so water boils at a lower temperature. For example, at sea level, water boils at 100°C, but at higher altitudes, it can boil at temperatures as low as 90°C or even lower. UPSC GS Paper-I PYQs 590 Reason (R) is false: Atmospheric pressure decreases with increasing altitude. As you go higher in the atmosphere, the air becomes less dense, and the pressure exerted by the atmosphere decreases. This is why mountaintops have lower atmospheric pressure compared to sea level. 248

Assertion (A): The boiling point of water decreases as the altitude increases. Reason (R): The atmospheric pressure increases with altitude.Codes:

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Assertion (A): The boiling point of water decreases as the altitude increases. Reason (R): The atmospheric pressure increases with altitude.Codes:

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