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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 sounds 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.

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    $\begingroup$ Are these blocks of dry ice allowed to be contained in something? Or do they have to be able to survive open to the room? $\endgroup$ – hBy2Py Apr 25 '17 at 3:48
  • $\begingroup$ Yes, I'd like them to survive in the open room. I don't know the difference between dry ice and the packages you buy from grocery stores by the way. All I'm looking for is ice (in smaller size 3x3x4 in) that can stay cold for 3-4 hours. I just want to know if that's possible. Thank you so much for your help. $\endgroup$ – Amanda J Apr 25 '17 at 14:43
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Put them in a container. It could be open at the top, but should be enclosed in the bottom.

The dry ice will insulate itself with a layer of cold air/CO2. As long as they are not under direct heating illumination or the convection of air in the room is high, this should be sufficient for a suitable mass of dry ice.

We routinely keep dry ice in "open" unpowered freezers at my lab (with no refrigeration) for the duration of the day. If your room is very humid you can get buildup of ice / condensed water, so some insulation around the container might be prudent.

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    $\begingroup$ As your dry ice is open to the air I hope that your lab is well ventilated! $\endgroup$ – porphyrin Apr 25 '17 at 7:23
  • $\begingroup$ Be very careful about putting dry ice in closed containers. If the seal isn't tight or the lid is left slightly ajar, it might be fine (though you still have to worry about ventilation), but if it does from a good seal (which can even happen accidentally from water/condensation freezing the lid shut), in the worst case scenario you are looking at a dry ice bomb. These can be dangerous even in something as innocent as a plastic bottle; I've seen people with mauled fingers from the shrapnel. $\endgroup$ – Nicolau Saker Neto Apr 25 '17 at 7:33
  • $\begingroup$ Make the container from expanded polystyrene and this will work for an extended period, possibly days if you have enough dry ice to start with. $\endgroup$ – matt_black Apr 25 '17 at 10:30
  • $\begingroup$ @porphyrin Yeah, I do not work in unventilated laboratories =) There are numerous alarms on numerous gases. As for OP's question I assume he understands the risks of carbon dioxide and death by respiratory acidosis, because he should have gotten (will get) that information where he got (will get) the dry ice. $\endgroup$ – Stian Yttervik Apr 25 '17 at 13:28

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