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vox
Joined: 13 Feb 2005
Location: Jeollabukdo
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 Posted: Mon Mar 12, 2007 5:40 pm Post subject: Science materials question |
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Hi
I'm prepping this demonstration for next Friday's immersion English class and I'm at a loss for a suitable replacement for something hot that I can put in our transparent plastic box.
This is an ESL immersion science class series on weather systems and air pressure. The demo calls for an aquarium (I'm using a plastic box), ice in one corner, warm sand in another corner, and lit incense in the middle. We then observe in which direction the smoke moves and discuss it.
My co-teacher suggested using a cup of hot water but I think the steam might interfere with the results. I can't figure out how I would get sand warm enough to have the desired influence. The ice is no problem.
Can anyone suggest something? I'm even looking around for those hotpockets (gel bags with a metal agitator inside you bend and gets the whole thing really warm)
Better yet has anyone done this? This lesson plan (from Busan or Jeollanamdo schoolboard) calls for a box with toilet paper rolls as chimneys. I think the open plastic box will be better.
edit: what happens if you put sand in the microwave? |
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mnhnhyouh
Joined: 21 Nov 2006
Location: The Middle Kingdom
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| Posted: Mon Mar 12, 2007 5:52 pm Post subject: Re: Science materials question |
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| vox wrote: |
edit: what happens if you put sand in the microwave? |
Microwaves only heat polar molecules, like water. The reason you have to go so slowly to defrost ice is that the bonds in ice remove much of the polarity and the water molecules cant absorb the microwaves.
The silica in sand is not polar, so microwaves wont heat it. If the sand is wet you could heat the water in the mix, and the sand would then absorb the heat from the water. Just as easy to pour boiling water over it thought.
If you have access to a bunsen burner or other type of gas, I would just dry roast the sand.
h |
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mnhnhyouh
Joined: 21 Nov 2006
Location: The Middle Kingdom
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vox
Joined: 13 Feb 2005
Location: Jeollabukdo
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| Posted: Mon Mar 12, 2007 6:22 pm Post subject: |
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Thanks for those, they're really interesting, especially the second.
It would be an open plastic box but I'm going to try it this afternoon with a hot water cup and ice next to it and see what happens. |
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vox
Joined: 13 Feb 2005
Location: Jeollabukdo
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| Posted: Tue Mar 13, 2007 8:13 pm Post subject: |
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I did a run of the demo today and I found the incense moved toward the cup of hot water. Actually it looked more attracted to it. So I don't think the right effect was achieved. I held the incense in the middle and it drifted over to the hot steam. But hot steam should be heavier than cold air, right? When I held it over the cold ice it didn't do anything unusual. And I had to put it right over the hot steam again for the smoke to be drawn toward that direction again. It's supposed to demonstrate that cold air is heavier than hot air. But I've got other materials for the class, too (pictures). I just want this to work.
It's close enough to what I want it to do, but I'm not sure this is a good demonstration. I'm thinking of trashing it and trying the differently- coloured and tempered waters. |
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vox
Joined: 13 Feb 2005
Location: Jeollabukdo
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| Posted: Mon Mar 26, 2007 11:19 pm Post subject: |
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Just for future reference, on the off chance someone is paying attention to this thread, if you abandon the ice, sand, and box altogether and just put the incense at the upper part of the crack of your classroom door, the smoke blows out (following warm air current) and if you place it at the bottom (making sure the hallway windows are shut) the smoke will blow inward, following the cold air current.
Infinitely easier. |
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