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If you melt dry ice, can you swim in it without getting wet?
Question Date: 2003-05-15
Answer 1:

Dry ice isn't frozen water- it is frozen carbon dioxide, and it "melts" directly to carbon dioxide gas , so there will be nothing to swim in. Most chemicals can exist as solid, liquid, or gas, and which of these three forms a chemical takes will depend on temperature and pressure. The temperature and pressure dependencies are different for each chemical. For example: at atmospheric pressure, water is solid below 32 degrees Fahrenheit and gaseous above 212 degrees Fahrenheit. On high mountains the air pressure is less, so water boils (becomes a gas) at lower temperatures- this is why things take longer to cook at high altitudes. High in the upper atmosphere where pressure is very low, water's boiling point is actually reduced all the way to its freezing point, so liquid water cannot exist. With carbon dioxide this critical pressure is much higher than atmospheric pressure, so liquid carbon dioxide cannot exist out in the open, even at sea level. It must be kept in a high-pressure tank.

Answer 2:

As it turns out, there isn't really any way to melt dry ice under normal circumstances.

Let's explain: the state of matter, gas, liquid, or solid, basically depends on its temperature and also the pressure By pressure, I mean how much force is pushing on it from all sides; we feel pressure from the atmosphere all the time. In fact, if we left the Earth's atmosphere (like on a space walk without a space suit), our skin would probably be damaged from trying to hold us together without air pressure to help (among other things -- the reduced pressure might also cause our blood to start turning to a gas -- good reasons for space suits!).

>Dry ice is carbon dioxide, CO2, which is a gas at room temperature and atmospheric pressure. If you stay at atmospheric pressure but make CO2 cold, it goes straight to dry ice -- solid -- instead of becoming liquid. There is no liquid form of CO2 at atmospheric pressure. I'm not sure, but I suspect you might be able to get liquid CO2 if you increased the pressure, though I doubt you would feel "wet" from it if you could stick part of yourself in it. To learn more about how CO2 goes straight from solid to gas, try looking up the word "sublimation".

Answer 3:

Dry ice is called dry ice because the solid turns to gas when heated, without turning into a liquid first. However, if we apply pressure and heat, we can turn it into a liquid, and sure, we can swim in it. We know this because of something called the phase diagram of carbon dioxide (the "stuff" of dry ice). It will be cold though !

Answer 4:

You cannot swim in melted dry ice because dry ice (frozen carbon dioxide gas) does not melt.

Instead of melting, dry ice "sublimates", which means it turns straight from a frozen solid into a gas. If you tried to jump into a pool filled with carbon dioxide gas, first you'd hit the bottom of the pool and then you'd suffocate.

It is true that most compounds have three phases -- solid, liquid and gas. However, for some compounds, one or more of those phases only occurs at special pressures. Carbon dioxide is a solid and a gas at normal (atmospheric) pressure depending on the temperature, but it is a liquid only at very high pressures. These are pressures you and I would normally never experience, and so we will probably never see liquid carbon dioxide. Where would you expect to find really high pressures on the earth?

Answer 5:

Molecules and atoms exist in certain physical forms (solids, liquids, and gases) on Earth because of the temperature and pressure that the earth has. The temperature and pressure varies depending upon where you live. But most molecules (except water) and atoms are in the same state no matter where on earth you are. For instance, carbon dioxide (CO2) is always a gas when in the earth's atmosphere . Carbon dioxide is a gas, unless it is cooled down to really low temperatures and under a lot of pressure. Dry ice is solid CO2. It is solid because it is pulled out of the air when the air gets really, really cold (way colder than the north pole!), and really, really high pressure.

Once the CO2 is a solid, it stays like that until you bring it out in the earth's atmosphere. Then you see it starting to "smoke". This is when it is going back to its normal state (gas) in the earth's atmosphere.

This process is called sublimation, which means that the molecule goes straight from the solid form to the gas form. Most molecules melt, where they go from being a solid to a liquid. Although it is possible for dry ice (CO2) to be a liquid, it would never exist like this under "normal" atmospheric conditions. So although it may be possible to get liquid CO2, you could never swim in it because it would be way, way to cold for you to survive. And if you did swim in it, you most certainly would be "wet".

Answer 6:

If you melt dry ice at normal atmospheric pressure -- you only get gas since liquid carbon dioxide has such a high vapor pressure. If you did your experiment under pressure -- say at the bottom of the ocean, it is possible to get a liquid, but you'd probably not want to swim in it, as you'd freeze very quickly. It might be possible to find a solvent in which you could dissolve a lot of CO2 (e.g. several liters of acetylene can be dissolved in a small amount of acetone) but it would still require pressure and still be fairly uncomfortable.

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