Curious Minds

Why doesn't water boil in a microwave?

Do you ever like cooking food or heat up water in a microwave oven? If yes, this article would make you aware of the harm that might be caused to your health by using microwave. In a microwave, the heating is due to the collision of microwaves (radio waves) unlike the heating that is done on a gas stove. These waves are absorbed by water, fats and sugars. When they are absorbed they are converted directly into heat which in turn heats up the food / water in the oven.

When water is being heated on a gas stove, the water particles at the base of the vessel are heated first. On heating, these particles become lighter than the cold water particles above them and hence they come up to the surface thus moving the cooler particles to the base. This cycle repeats till all the particles in the vessel are uniformly heated and once the temperature of the water particles reaches 100oC, the water starts boiling.

In case of the water being heated in a oven, the water in the vessel does not heat up uniformly. Also, since all of the particles are at uneven temperatures, the warmer particles never come up to the surface. The water lining the sides of the container becomes heated quickly, while some of the water toward the interior of the container still remains cool. Thus though the water temperature goes higher than the boiling point, the water doesn't start boiling due to the temperature variation.

When such unevenly heated water is taken out of the microwave after heating for long, a sudden temperature variation causes the water to become unstable. Due to this, the particles strive to achieve a stable state in a short span of time. If this balance is disturbed by performing some unusual activity like inserting a spoon or any object inside water or tilting the glass, the hot water suddenly rushes to the surface pushing the cooler particles down. The splashing of this hot water may result in serious injury causing blisters on the skin.

Here are some of the safest methods of heating water in a microwave -

  • Put spoon (Non-metallic) or a wooden stick in the glass with water before heating.
  • Keep stirring the water at short intervals so as to neutralize the uneven temperature till the water is heated.
  • Allow the water to stay in the microwave for some time after the heating is complete by keeping the door of the oven open.

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