A pressure cooker can be used to cook food more quickly than traditional methods
ID: 474770 • Letter: A
Question
A pressure cooker can be used to cook food more quickly than traditional methods. Using the Clausius-Clapeyron equation as a starting point, develop a model equation that allows you to calculate the boiling point of water at any given pressure. Pressure cookers generally cook at double to triple the pressure of the surroundings, so generally the pressure within would be approximately 2.5 atm. At that pressure, use your model to determine the temperature that food would cook within a pressure cooker. Conceptually, explain in words that a high school student can understand why a pressure cooker can help to cook food more quickly?Explanation / Answer
Classius -Clayperon equation is
ln(P2/P1)= (deltaH/R)*(1/T1-1/T2)
where P2= vapor pressure at the given temperature T2, P1= vapor pressure at temperature T1. R=gas constant = 8.314 J/mole.K
deltaH= latent heat of vaporizatino of water =40.5Kj/mole= 40.5*1000 J/mole. Asssumed to be indepenndent of pressure. ( this is one of the assumptions made in deriving the classius-Clayperon equation)
2. at T1= 100 deg.c= 100+273=373K P1= 1atm and P2= 2.5 atm T2=
ln(2.5/1)=(40.5*1000/8.314)*(1/373-1/T2)
0.000188= 1/373-1/T2
1/T2= 0.002493, T2= 401K= 401-273= 128 deg.c
2. Pressure cooker is a closed system and the increase in pressure energy is transferred to liquid water and even though liquid boils at high temperature, there are no heat losses compared to cooking at atmospheric pressure . So the heat energy is effectively utilized in case of pressure cooker leading to less time for cooking.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.