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Topic: I have a question, don't know where to ask, please help...  (Read 2107 times)

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Amanda93

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I have a question, don't know where to ask, please help...
« on: April 24, 2017, 10:02:46 PM »
Hello,

I have a chemistry question but I'm not sure which subtopic it'd go under, so I'm asking it here. I'd really appreciate any help I can get, if you have an answer, or if you can tell me where I can find the answer. I should also mention I don't know anything about chemistry, so I'm sorry if my question sound stupid :-)

I was wondering if it's possible for dry ice  (the industrial ones or those that are sold at stores) to stay cold/frozen in a rather warm/hot room temperature for around 2-4 hours. Let's say blocks of 3x3x4 inches. I just want to know if that's feasible or not.

Thank you so much for your help,

Amanda (Mandy)

Offline Arkcon

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Re: I have a question, don't know where to ask, please help...
« Reply #1 on: April 25, 2017, 05:09:43 AM »
So you want to put some blocks of dry ice into a cooler, and keep them a while, somewhere ... warm.  If you put them in a Styrofoam cooler, what you have is a calorimetry problem, we get those here often.

I hate computing those.

Anyway, you have a certain mass (chucks of a certain thickness isn't specific enough I'm afraid) you can look up dry ice's heat capacity, you know its starting temperature, and you know the temperature of the "warm" room (we need numbers to compute.) 

Maybe you better just try it and see.  Or ask the dealers of dry ice.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Corribus

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Re: I have a question, don't know where to ask, please help...
« Reply #2 on: April 25, 2017, 09:49:55 AM »
If it's kept in a reasonably well insulated container (e.g., styrofoam), a large quantity of dry ice will stay frozen for quite a while. I mean, it's used for shipping temperature-sensitive materials for a reason. The evaporation rate is dependent on a lot of factors, though, so it's not really possible to generalize.

Before you use dry ice, I recommend taking a moment to review safe handling procedures.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Amanda93

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Re: I have a question, don't know where to ask, please help...
« Reply #3 on: April 25, 2017, 10:11:33 AM »
Thank you for your replies. I mean out in the room, not in the cooler. I was wondering if it is possible for them to stay cold for 2-4 hours like that.

Offline Corribus

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Re: I have a question, don't know where to ask, please help...
« Reply #4 on: April 25, 2017, 11:33:22 AM »
It would depend on the size and shape of the block and the temperature of the room. A single pellet probably wouldn't stick around for two hours but a 50 pound brick probably would. My college physical chemistry professor had a saying that has stuck with me: "An experiment is worth a thousand predictions."
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline kriggy

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Re: I have a question, don't know where to ask, please help...
« Reply #5 on: April 28, 2017, 01:46:23 AM »
It stays for reasonable long time if you put it into isolated container - polystyrene box seems cheapest. We get some 10 kg of dry ice every week and I think it would survive a few days in the box

What is your application?

also note that dry ice is pretty cool so dont touch with bare hands, use some kind of showel instead.

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