WAEC SSCE - Physics - 1989 (Objective)

Question 1 Report

Water in an open container boils at a lower temperature when heated at the top of a mountain than at sea-level because at the top of a mountain the

relative humidity is higher than at sea-level

rays of the sun adds more heat to the water

temperature is lower than that at sea-level

pressure is lower than that at sea-level

pressure is more than that at sea-level

Answer Details

Water in an open container boils when the vapor pressure of the water equals the atmospheric pressure. At higher altitudes, the atmospheric pressure is lower than at sea-level because the column of air above is shorter. As a result, water boils at a lower temperature at higher altitudes because the lower pressure means that water molecules need less thermal energy to break the intermolecular bonds and evaporate into the air. Therefore, the correct option is that at the top of a mountain, the pressure is lower than that at sea-level, leading to a lower boiling point of water.






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