I have observed this while cooking, but if you boil something at high flame and then turn the flame low, the liquid stops boiling. E.g. Water boils at 100C. On high gas, it starts boiling. That means the water temp is now 100C. Then if I lower the flame, the water stops boiling even though the flame temperature is greater than 100C at all times. At high flame, the water has reached 100C, so if I lower the flame the water temp should still remain 100C.
In: Physics
To start with, heat equals energy. There are several areas in which energy is lost between the end of the flame, and the water to be boiled in the pot. The flame heats the air around it, as well as the pot. The pot in turn heats the air around it that wasn’t heated by the flame, as well as the water inside the pot. So, not all of the energy in the flame makes it to the water in the pot.
Assuming these losses have been overcome, the reason turning the flame down causes the water to stop boiling is due to a property known as heat of vaporization. This is the energy needed to turn water at 100C to steam at 100C. For water, this is 586 calories. This means that it takes 586 times as much energy to make steam as it does to raise the temperature of the water from 99C to 100C.
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