Why are pressure cookers faster than open cooking?
Show answer & explanation
Correct answer: C
Explanation
Solution: The correct answer is Increase water's boiling point.
Explanation:
☛ Under normal atmospheric pressure (1 atm), pure water boils at 100°C (212°F).
☛ In an open vessel, the temperature of boiling water cannot exceed its boiling point because excess heat is lost through vaporization.
☛ In a sealed pressure cooker, steam is trapped inside, which significantly increases the internal pressure.
☛ An increase in external pressure raises the boiling point of water from 100°C to approximately 120°C (248°F).
☛ Because the water and steam reach higher temperatures without boiling away immediately, heat penetrates the food faster, drastically reducing cooking time.
Extra Exam-Relevant Facts:
☛ High Altitudes: Atmospheric pressure is lower in mountainous regions, so water boils at a temperature below 100°C, making cooking in open pots much slower.
☛ Denis Papin: The prototype of the modern pressure cooker, called the "Steam Digester", was invented by French physicist Denis Papin in 1679.
☛ Gay-Lussac's Law: This law states that the pressure of a given mass of gas is directly proportional to its absolute temperature at constant volume (P ∝ T).
☛ Safety Valve: A weighted valve (whistle) on the lid regulates internal pressure and prevents explosions by venting excess steam.
Important One-Liners for Upcoming Exams:
☛ What happens to the boiling point of water at high altitudes? → It decreases due to lower atmospheric pressure.
☛ Who invented the earliest prototype of the pressure cooker called the "Steam Digester"? → Denis Papin.
☛ What is the boiling point of pure water at sea level on the Kelvin scale? → 373.15 K.
☛ Which gas law relates the pressure and absolute temperature of a gas at constant volume? → Gay-Lussac's Law.
☛ What happens to the melting point of ice when pressure is increased? → It decreases.