DENJIRO: Here’s what we’re going to look at today.
BOY: That’s some tasting looking curry!
DENJIRO: No, our topic today isn’t curry. It’s the pressure cooker that was used to cook it. You can cook something in a short amount of time using a pressure cooker. Let’s perform an experiment to see how it works.
This flask has water in it. I’m going to boil the water. The water’s boiling now. Let me measure the temperature. It’s 100 degrees Celsius. At regular atmospheric pressure, or 1 atm, water doesn’t go over 100 degrees regardless of how much you heat it. The reason is the bubbles that come out when water is boiling. This is water vapor from the water turning into a gas. When water turns into water vapor, thermal energy is lost, so it doesn’t go over 100 degrees.
Now let me put a rubber stopper with a pressure gauge on the flask.
BOY: Huh? It went over 100 degrees.
DENJIRO: Sealing the flask with the rubber stopper caused the pressure inside to rise. The pressure gauge is pointing at 0.02. This shows that the pressure inside the flask is now 1.2 atm. The temperature has reached 106 degrees as well. When pressure inside the flask rises, water is pushed down, making it harder for water vapor bubbles to be produced. As a result, continuing to heat it causes thermal energy to be used for raising the temperature. Therefore, the temperature goes over 100 degrees. A pressure cooker uses this principle.
A pressure cooker is tightly sealed to raise the pressure inside. That way, you can cook at temperatures over 100 degrees. As a result, the cells of meat and vegetables are broken down in a shorter amount of time. You can soften hard foods and shorten the cooking time this way.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!"