Ques. 1AIPMT 2001
The beans are cooked earlier in pressure cooker because
- boiling point increases with increasing pressure
- boiling point decreases with increasing pressure
- extra pressure of pressure cooker softens the beans
- internal energy is not lost while cooking in pressure cooker
Answer
(1) boiling point increases with increasing pressure
Solution
A liquid boils when its vapour pressure becomes equal to the external pressure.
⇒ In a closed pressure cooker the pressure above the water is more than 1 atm, so the water must be heated to a higher temperature (about 120 C) before it boils.
⇒ As per NCERT, liquids boil at lower temperatures when the pressure is low (e.g. at high altitudes), which is why a pressure cooker is used for cooking food there.
∴ Boiling point increases with increasing pressure, and the beans cook faster at the higher temperature.
Answer: (1)
Out of syllabus