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Why Pressure cooking at high altitude takes more time?

It is a little bit complicated to answer this question ” Why cooking at higher altitude takes more time?. As we go at a higher and higher altitude, the atmospheric pressure decreases. This decrease in Pressure cooking at high altitude is due to two reasons.

Explanation about Pressure cooking at high altitude

First of all, about half of the atmosphere’s molecules are located below 5.5 km, so there are fewer molecules at higher altitude. 

Secondly, at a higher altitude, the molecules are far apart from each other. As the earth’s gravitational attraction on molecules weakens and molecules cannot be bounded to remain close to each other and if you want information about Microwave Oven then you are right place .

This causes a decrease in the density of air at higher altitude. And according to the formula P = GH, a decrease in density implies that the pressure will also decrease in a similar manner.

Vapour pressure

First, this pressure will decrease rapidly and then slowly. The vapours exert the pressure of the liquid at the surface of the liquid when we provide heat to the water

Vapour pressure is the tendency of liquid to change into the vapour state. It does not depend on atmospheric pressure. But the vapour pressure and atmospheric pressure together influence the boiling point of the liquid. Boiling point is the temperature at which the vapour pressure of the liquid becomes equal to the atmospheric pressure and the liquid starts boiling.

At sea level, the boiling point of water is 100℃ because it takes more time and more heat for the vapour pressure of the water to become equal to the atmospheric pressure of 760 atm. But at a higher altitude, it requires less heat and less time to equalize the vapour pressure of liquid with the atmospheric pressure.


Hence the liquid starts boiling at a much lower temperature which results in a decrease in the boiling point of the liquid. For example, the atmospheric pressure at Murree hills (Pakistan) is 0.9atm and the boiling point of water is 98℃. 

Similarly at Mount Everest, the atmospheric pressure is 0.3atm and the boiling point further decreases to 71℃. Apparently, one would think that decrease in boiling point will make cooking easy as it will require less time but the reality is quite contrary to this.

When the liquid will boil early, it will become difficult to transfer heat to the food ingredients in the water and resultantly they will remain uncooked at the end.

No matter how much heat we provide to the water, a great proportion of it will be used to break the intermolecular forces between the water molecules. Which is the liquid state to convert it into the Vapor state. And hence it will take a lot of time to cook the food.

Thus cooking food will take more time at higher altitude regions like hilly areas. But just like many other problems, this daily life problem has also been solved by technology. Pressure Cookers are essential kitchen tools in every household. They are the need of the modern era.

Vessel and trapping

It works by expelling air from the Vessel and trapping steam produced from the water boiling inside.

Hence this increases the internal pressure in the cooker which raises the boiling point. Allowing sufficient heat to reach the food particles. Hence Pressure Cookers make cooking easy at higher altitudes. In some cases, this may behave opposite.

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