It takes much longer to cook food in the hills than in the plains, because. In the hills the atmospheric pressure is lower than in the plains and therefore water boils at a temperature lower than the 100oC causing an increase in cooking time.

As the pot is heated, the temperature inside increases until the water starts to boil. At that pressure, water boils at 121°C (250°F). That means food can cook at a much higher temperature than it ever could at atmospheric pressure—and since cooking reactions speed up at higher temperatures, your food cooks faster.

At a higher elevation, the lower atmospheric pressure means heated water reaches its boiling point more quickly—i.e., at a lower temperature. But the fact that the boiling temperature is lower at higher elevations means food takes longer to cook, which is where the confusion lies.

On mountains, the atmospheric pressure is less. Therefore, the boiling point of water is less than the normal boiling point of water in mountains. Pressure cooker increases pressure and thus the boiling point of water increases than the normal boiling point of water due to which cooking takes less time.

The key factor is declining air pressure at higher altitudes. Falling air pressure lowers the boiling point of water by just under 1 degree Fahrenheit for each 500 feet of increased elevation. The lower boiling point means water will cook off more quickly, and at a lower temperature.

As altitude increases and atmospheric pressure decreases, the boiling point of water decreases. To compensate for the lower boiling point of water, the cooking time must be increased. Turning up the heat will not help cook food faster.

At high altitude pressure is low and therefore the boiling point is also low. In this case, water starts boiling below its boiling point but rice cooks at 100. So, it is difficult to cook rice at high altitudes.

As altitude rises, air pressure drops. In other words, if the indicated altitude is high, the air pressure is low. As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level.

Pressure: when the external pressure is: less than one atmosphere, the boiling point of the liquid is lower than its normal boiling point.

ice melts faster than water boils because it takes longer for a liquid to become a gas than for a solid to become a liquid.

Answer. It takes longer to boil water than to melt ice because of the difference in the amount of heat required to overcome the forces of attraction by keeping the temperature constant during this time.