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  4. How does microwave superheat water?
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How does microwave superheat water?

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Online Bored chemist

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Re: How does microwave superheat water?
« Reply #100 on: 24/04/2022 10:30:37 »
Quote from: hamdani yusuf on 23/04/2022 23:08:35
The ceramic plate filters out some wavelengths.
By Kirchhoff's law, the ceramic plate does exactly as good a job of re-emitting those wavelengths as it does of absorbing them.
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Offline hamdani yusuf (OP)

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Re: How does microwave superheat water?
« Reply #101 on: 24/04/2022 11:22:17 »
Quote from: Bored chemist on 24/04/2022 10:30:37
Quote from: hamdani yusuf on 23/04/2022 23:08:35
The ceramic plate filters out some wavelengths.
By Kirchhoff's law, the ceramic plate does exactly as good a job of re-emitting those wavelengths as it does of absorbing them.

The ceramic plate doesn't glow red. It's significantly cooler than the heating element.
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Re: How does microwave superheat water?
« Reply #102 on: 24/04/2022 11:25:04 »
Quote from: hamdani yusuf on 22/04/2022 10:53:06
Do you think gas stove will give better result?
It looks like I have to do the experiment myself, just as usual.
I've done recording the video, and I'll upload it after I finish the editing.
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Re: How does microwave superheat water?
« Reply #103 on: 24/04/2022 14:07:33 »
Quote from: hamdani yusuf on 24/04/2022 11:22:17
Quote from: Bored chemist on 24/04/2022 10:30:37
Quote from: hamdani yusuf on 23/04/2022 23:08:35
The ceramic plate filters out some wavelengths.
By Kirchhoff's law, the ceramic plate does exactly as good a job of re-emitting those wavelengths as it does of absorbing them.

The ceramic plate doesn't glow red. It's significantly cooler than the heating element.
So the fact that visible light  goes through borosilicate is even less relevant.
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Re: How does microwave superheat water?
« Reply #104 on: 25/04/2022 15:36:38 »
Quote from: Bored chemist on 24/04/2022 14:07:33
So the fact that visible light  goes through borosilicate is even less relevant.
The ceramic plate is somewhat transparent to red light, as shown in the video. So, the water receives some red and infrared radiation, beside the heat conduction from the borosilicate glass.
The difference from microwave oven is that the borosilicate glass generates almost no heat from the radiation. The heat is generated in the water instead.
« Last Edit: 25/04/2022 15:46:11 by hamdani yusuf »
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Re: How does microwave superheat water?
« Reply #105 on: 25/04/2022 16:33:27 »
Quote from: hamdani yusuf on 25/04/2022 15:36:38
So, the water receives some red and infrared radiation,
And the red light goes straight trough the water- because water is colourless.

What point are you trying to make?
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Re: How does microwave superheat water?
« Reply #106 on: 26/04/2022 03:45:59 »
Quote from: Bored chemist on 25/04/2022 16:33:27
Quote from: hamdani yusuf on 25/04/2022 15:36:38
So, the water receives some red and infrared radiation,
And the red light goes straight trough the water- because water is colourless.

What point are you trying to make?
Identify all differences and similarities between microwave oven and infrared stove in boiling demineralized water inside a smooth container. Then identify which differences contribute to the difference in their result regarding superheating of water.
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Re: How does microwave superheat water?
« Reply #107 on: 26/04/2022 08:06:18 »
Quote from: hamdani yusuf on 26/04/2022 03:45:59
Quote from: Bored chemist on 25/04/2022 16:33:27
Quote from: hamdani yusuf on 25/04/2022 15:36:38
So, the water receives some red and infrared radiation,
And the red light goes straight trough the water- because water is colourless.

What point are you trying to make?
Identify all differences and similarities between microwave oven and infrared stove in boiling demineralized water inside a smooth container. Then identify which differences contribute to the difference in their result regarding superheating of water.
OK the so called infrared stove does shine a small amount of red light through the water.
Do you think that is likely to have an effect?

What are the power ratings of the two systems?
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Re: How does microwave superheat water?
« Reply #108 on: 26/04/2022 12:32:34 »
Quote from: Bored chemist on 26/04/2022 08:06:18
OK the so called infrared stove does shine a small amount of red light through the water.
Do you think that is likely to have an effect?
A similarity between infrared stove and microwave oven : Some heat is generated in the water.
A difference: Most heat in boiling water by infrared stove is generated in the glass body, which is then transferred to water through conduction. Whereas most heat in boiling water by microwave oven is generated in the water itself.
Although it hasn't been obvious yet that the difference above is the one which causes the different result.
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Re: How does microwave superheat water?
« Reply #109 on: 04/05/2022 09:40:54 »

Here's the experiment of boiling demineralized water in borosilicate beaker using gas stove. It seems that lack of nucleation site can still make it boil. No superheating is shown.
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Re: How does microwave superheat water?
« Reply #110 on: 04/05/2022 13:19:12 »
At about 37 seconds you imply that my breath is at 100C on a cold day.

Your experiment shows that heating water from the bottom is less likely to cause superheating than if you heat it throughout.
So what?

In reality, superheating was documented long before anyone had microwave ovens.
So it is clearly possible to superheat water without using microwaves.

Do you accept that?
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Re: How does microwave superheat water?
« Reply #111 on: 05/05/2022 03:27:47 »
Quote from: Bored chemist on 04/05/2022 13:19:12
At about 37 seconds you imply that my breath is at 100C on a cold day.
How would you interpret the condensation there?

Quote from: Bored chemist on 04/05/2022 13:19:12
Your experiment shows that heating water from the bottom is less likely to cause superheating than if you heat it throughout.
So what?
The fire clearly touches the side of the beaker as well.

Quote from: Bored chemist on 04/05/2022 13:19:12
In reality, superheating was documented long before anyone had microwave ovens.
So it is clearly possible to superheat water without using microwaves.
What's your evidence? A video may be?
Do the superheated water by other means behave the same way as superheated water by microwave oven?
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