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Q & A: CO2 and bottles

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Most recent answer: 10/22/2007
Q:
I am doing a science progect. I have done an experiment of putting dry ice and water in a plastic bottle then we put the lid on. We think that co2 Gas was relised witch caused the bottle to expand and pop. We would like more information on this subject. I read on another web site that this may deminstrate the Sublimation Process we would like to know more about this process. I also would like to know what caused the loud pop. We think the the gas inside the bottle was relised so quickley that a sonic boom was the result. We would like any information you could send. Thanks, Brett
- Brett Courtney (age 14)
Lawrence Kansas
A:
Hi Brett,

Dry ice is the common name for solid CO2. The temperature of dry ice is about -78.5 C, and the water you used in your experiment was probably somewhere around normal room temperature (25 C). The water is very warm relative to the dry ice so the solid CO2 begins to "melt," but unlike water, which changes from a solid to a liquid before turning into a gas, CO2 changes directly from a solid to a gas at normal atmospheric pressure. This process is known as sublimation.

As the dry ice sublimes, the pressure inside the bottle increases because gases take up more space than solids. At some point, the bottle is no longer able to withstand the pressure that has built up inside, and it bursts. The loud popping sound is caused by the high pressure air that was previously inside the bottle suddenly pushing on the normal pressure air around it, creating a pressure wave that is detected by your ears and interpreted as sound. (This is different from a sonic boom, which is caused by objects moving faster than the speed of sound.)

By the way, blowing up bottles this way is kind of dangerous...please be very careful!

Thanks for your question!

(published on 10/22/2007)

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