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The original title: "what happens when water and ice go into the microwave oven together?" You can't be the last to know. "

Write an article | Seven Jun

Put the water and ice in the microwave oven together for 3 minutes. If the water is already smoking, will the ice melt?

Actually, it's not.

If you don't believe me, take a look at this video.

(photo source: watermark) the blogger put a glass of water and a glass of ice in the microwave oven and heated it for 3 minutes at the same time. As a result, the water has begun to vaporize and the ice is still ice.

The video broke through the common sense of many people and went viral on the Internet and has been viewed thousands of times.

What's going on? It's not upside down, is it?

In fact, this water is real water, ice is also real ice, short video is also really hot. So why can't the microwave melt the ice? Isn't there a deicing stall in the microwave?

Today we are going to answer this secret common sense.

(photo Source: wikimedia) things start with the principle of the microwave oven.

Unlike ovens, microwave ovens do not directly transmit heat to heat food. Microwave heating depends on the polar molecules in the food, because polar molecules can "eat" microwaves.

Specifically, microwave is a kind of electromagnetic wave, and the changing electromagnetic wave can "draw" the magnetic induction line in the microwave oven, which we learned in middle school.

While polar molecules are positively charged at one end and negatively charged at the other, they are like magnets, always trying to align with the magnetic induction line. But they're always too late in the microwave.

Dielectric heating (photo source: watermark) because the magnetic field in the microwave oven can change millions of times per second. Imagine what would happen if the instructor asked the military training students to turn forward and backward a million times per second. The students will probably bump their heads and bleed each other. The same is true of polar molecules, but they don't bleed, they get hotter and hotter. This physical phenomenon, which uses changing electromagnetic fields to cause particles to collide to generate heat, is called dielectric heating (dielectric heating).

So, where can we find such tumultuous polar molecules?

In fact, they are everywhere. Water molecules are polar molecules, and fat, protein and sugar molecules can also spin around in the microwave oven.

Water molecules in a changing electric field (photo source: radio frequency co) so the question is, isn't ice made up of water molecules? Why does microwave have no effect on ice?

In fact, this problem was noticed as early as the 1990s. In 1995, the Physics Department of the University of Virginia explained that water molecules in liquid water could move freely, so they could go crazy in changing electromagnetic fields.

But ice is more restrained, because ice is a crystal formed by water molecules "locked" to each other, and the water molecules in it cannot rotate happily, so they cannot generate the same heat as free water molecules under the same conditions.

The difference of water molecules between water (left) and ice (right) (Photo: wikimedia) for the ice to be microwaved, only some free water molecules on the ice surface can produce heat after absorbing the microwave. When these molecules become active, they become freer, generate more heat, and then transfer the heat to the internal ice crystals, allowing the ice to gradually melt. That's why microwave ovens can't thaw quickly.

After the blogger drips the dyed ice water into the ice cubes and heats it in the microwave, it is obvious that water heating causes the ice to melt, not the other way around (photo source: Greg Blonder / youtube) apart from the difference between water and ice, microwave ovens are difficult to melt ice and actually involve some other flaws in microwave ovens.

First of all, because microwaves are also electromagnetic waves, they will interfere with each other, resulting in enhancement in some places and weakening in some places, that is, mutual interference and cancellation interference, which will lead to uneven heating of food.

The U.S. Department of Agriculture's Food Safety Inspection Service (FSIS) stressed that microwave heating is not uniform and that food will have a "cold spot" (cold spots). Because these areas are not sufficiently heated, bacteria may not be killed and may cause food poisoning.

The food heated by microwave has cold spots (purple) (photo source: campdenbri.co.uk/ blogs / solid-state-microwaves.php). Of course, manufacturers also know that microwave ovens have this problem, in order to avoid microwave cancellation cold spots (wave joints) can not heat food, microwave ovens usually bring their own turntable.

After heating in the microwave oven for 25 seconds, the difference between no rotation (left) and rotation (center) and the low temperature in the purple zone (Photo: genuine ideas) the second drawback of the microwave oven is that the penetration of the microwave is so poor that the food is not directly heated inside.

The USDA Food Safety Inspection Service (FSIS) explained that microwaves do not have a strong penetration and can only go 2-4 cm below the surface of the food, and the internal heating of the food is achieved by heat conduction.

To sum up, this is why the ice at the beginning of the article does not melt. Of course, this is why when frozen food is heated in the microwave, some parts are still cold, but some places that already have water are so hot. So when cooking in the microwave oven, especially when cooking with large chunks of raw meat, be sure to cut small pieces and turn them over and over again.

(photo source: wikimedia) you might ask, since microwave ovens are not good at melting ice, what is the principle of microwave ovens with "thawing" files?

In fact, the working principle of microwave oven thawing gear is to start and stop, by sacrificing time, let the food melt out part of the liquid water, and then heat it.

Wait a minute, why don't microwave ovens use low-grade microwave firepower heating?

This is another deeply hidden cold knowledge: traditional microwave ovens have only two gears-on and off, and the so-called different firepower is achieved through duty cycle (Duty Ratio), which simply means turning on and off for a while.

The firepower control principle of traditional microwave ovens depends on duty cycle: switching on and off (photo source: panasonic.hk) for example, 50% firepower means turning on half the time, turning off half the time, rather than turning on at half the power. Of course, there are some frequency conversion microwave ovens that can be pulled down without duty cycle, just like ovens.

Finally, I would like to remind you that in addition to ice, some food is not suitable for the microwave oven.

Raw grapes produce arcing in the microwave oven (photo source: wired) needless to say, raw grapes can not enter the microwave oven, which produces arc (arc), which causes the gas to break down into plasma. Grapes plus microwave, lightning under the hot pot.

Carrots arc in the microwave (photo: Stefonivich / youtube), but the other two unpopular ingredients are also fierce.

Raw carrots can also add fire and lightning in the microwave, but the principle behind it has not yet been understood. According to the U.S. Department of Agriculture's Food Safety Inspection Service (FSIS), this may be caused by metals in the soil of carrot cultivation. In addition, hot dogs also arc in the microwave, which may be due to some salt and additives added to the hot dogs.

It is even less advisable to put carrots, hot dogs and grapes in the microwave oven. Those who know how to do it know that you are in a lightning meeting, while those who don't know think you are alchemy with a microwave oven.

Water already produces "steam", but ice is not "moved".

Cover source: wikimedia

Reference:

Https://docs.qq.com/doc/DVE9mdFlSWE9aZEJy

This article is from the official Wechat account: bring Science Home (ID:steamforkids), author: everything.

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