Science

2008-08-14 5:33 am
(Why doesn't the temperature of water rise any more at the boiling point?)

Water boils at around 100。C under normal air pressure . If we continue to boil the water , will the temperature of the boiling water exceed 100。C ? Experiments show that no matter how vigorously you boil the water , the temperature of the
boiling water still stay at 100。C .

Although water keeps on taking in heat from the flame while boiling , the heat taken in is carried into the surroundings by steam and will not be trapped inside the boiler . The hotter the flame is , the more the water will evaporate . As a result , the
temperature of water will not change any more at its boiling point. If so, are there any ways to increase the boiling point of water ?
Increasing the air pressure can raise the boiling point of water . This is because the air pressure above the water surface will hinder the movement of water (steam) into the air . When the air pressure increases, the boiling point of water also increases
as the water vapours have to overcome the air pressure and turn into steam. Therefore, the boiling point of water changes with the air pressure .
The pressurized cooker was invented based on his principle. When water boils, it turns into steam and is trapped inside the cooker. As the amount of steam in the cooker increases , the air pressure above the water surface also increases , causing
the temperature of water to become higher . Thus , the food can be cooked more quickly . However, the cooker may explode if the steam pressure inside is too high , so safety valves must be installed . When the steam pressure inside the cooker
iss higher than a certain level , part of the steam will be released to the air through the valve . This keeps the pressure in the cooker the same throughout the heating process .

Questions:

1.Under normal air pressure , at what temperature does water boil ?
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回答 (1)

2008-08-17 3:01 am
✔ 最佳答案
The first sentence of the text has already given you the answer.

'Water boils at around 100。C under normal air pressure'


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