# Science Officer, report to the Bridge. \[question about freezing water\] **URL:** \ **Category:** Factual Questions\ **Created:** [July 13, 2011, 11:54pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945 "2011-07-13T23:54:43Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [July 15, 2011, 2:44pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/21 "2011-07-15T14:44:30Z")
If any leakage into the vehicle is unacceptable, find/make a serviceable plug for the cooler drain or get a different cooler. Note that even with no leakage, condensation may result in a wet spot under the cooler. You might want to lay it on some towels, and maybe even line it with towels as your ice bottles will develop condensation. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 15, 2011, 3:30pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/22 "2011-07-15T15:30:21Z")
> [@Oly](#): > > It’s been a while, and an undisclosed number of similar “road trips”, since my p-chem days, but nevertheless… IIRC, when salt water freezes the salt is largely excluded from the ice crystals. So, frozen salt water is for the most part frozen fresh water with some salt on the side. Since that salt takes up space in the container, 1 liter of frozen salt water would result in less ice than 1 liter of frozen fresh water. That alone would reduce the “BTU stuff and shit” (or cooling capacity). Not sure about that - salt dissolves into water without increasing the volume considerably (which is why salt water is more dense than fresh, and why things float better in the sea) ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 15, 2011, 4:40pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/23 "2011-07-15T16:40:30Z")
And the salt will get cold too. It’s no going through a phase change, so it’s not as effective at cooling as melting ice is, but it will still absorb heat. But there is just no need for the salt in the first place. He’s not making old fashioned ice cream. The unsaid part is that a solid bodied cooler will be relatively inefficient. The best way to get cooler efficiency is to remove the air space inside. If that’s not done with loose ice or tightly packing it with whatever the hell he’s keeping in there, a soft-sided cooler will be more efficient, and less likely to leak, because the ones I’ve seen have no drain hole pluggy thing that he’s missing. ---
**Author:** ![Oly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/oly/32/8255_2.png) [@Oly](https://boards.straightdope.com/u/Oly)\ **Post date:** [July 16, 2011, 12:38am UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/24 "2011-07-16T00:38:37Z")
> [@Mangetout](#): > > Not sure about that - salt dissolves into water without increasing the volume considerably (which is why salt water is more dense than fresh, and why things float better in the sea) Yes, “salt on the side” should really be salty water on the side. I may be wrong, but wouldn’t this happen: The salt water would start to freeze at the freezing point determined by the salinity of the starting solution. As the water freezes, much of the salt would be excluded from the ice, which would then increase the salinity of the surrounding saltwater. If the temperature drops more, same would happen. Eventually, assuming you don’t have a freezer that would reduce the temperature past the freezing point of saturated saltwater, the freezing would stop and you’d be left with a certain amount of variably salty ice, plus a certain amount of really salty water. Since the water in the really salty water isn’t frozen, and all the water in the freshwater would be, you’d still be left with less ice when freezing saltwater than when freezing freshwater. ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [July 16, 2011, 2:38pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/25 "2011-07-16T14:38:39Z")
Let’s make some unfounded assumptions and see where it leads us. First, that the energy flux through the walls of the cooler is constant regardless of the temperatures inside and outside. Second, that the salt water is fully saturated NaCl brine, and it remains saturated regardless of temperature. Brine has a freezing point of -21.1º C, and a specific heat that is only about 77% that of fresh water. I can’t find a quick reference for the specific latent heat of fusion of brine, but let’s assume that, like the lower specific heat, it has a lower latent heat of fusion than freshwater. Therefore it takes less heat to melt a kilo of brine ice than a kilo of freshwater ice. If equal masses of freshwater ice and brine ice start in two coolers at the same very low temperature, say -30º C, then the brine ice will rise in temperature more quickly than the freshwater ice. At -21.1º C, the temp of the brine ice will plateau for a while until it is all melted, at which point it will start to rise again. Meanwhile, the freshwater ice continues to increase in temp until it hits 0º C, at which point it also plateaus, _for a longer period than the brine ice_. Once they are both melted, the temp of both liquids rises over time again, with the slope of the brine temperature vs. time being greater than the slope of the freshwater temperature vs. time. Thus, both coolers start at the same temp; the brine cooler gets warmer than the ice cooler immediately, but then plateaus and is passed by the freshwater cooler. Then the freshwater cooler plateaus and the brine cooler catches up and passes it. Then both coolers continue to heat up, with the brine cooler heating up faster than the freshwater cooler. So, if you want to keep your beer supercold for a short period of time, use frozen brine. If you want to keep it at not-quite-so-cold temperature for a longer period of time, use freshwater ice. Note that the freezing point of beer itself is about -2 or -3º C, and keeping it colder than that is just asking for slushy beer trouble. If your trip will be so long (or your cooler is such a poor insulator) that you expect that any freshwater ice will have melted by the end, you can be assured that any brine ice will also have totally melted and furthermore the brine cooler would be warmer by that point. ---
**Author:** ![The\_Man\_In\_Black](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@The\_Man\_In\_Black](https://boards.straightdope.com/u/The_Man_In_Black)\ **Post date:** [July 17, 2011, 3:03pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/26 "2011-07-17T15:03:37Z")
I freeze plastic bottles of water all the time. Sealed bottles straight from the store. They don;t bust. ---
**Author:** ![wbeaty](https://avatars.discourse-cdn.com/v4/letter/w/439d5e/32.png) [@wbeaty](https://boards.straightdope.com/u/wbeaty)\ **Post date:** [July 17, 2011, 9:17pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/27 "2011-07-17T21:17:27Z")
> [@UncleFred](#): > > Just curious - is this safe? If he’s driving with the windows closed, and a CO2 block fully or even partially sublimates - is releasing all that CO2 into the cabin OK? Modern vehicles include legislated required ventilation. Otherwise the tiniest exhaust leak into the cab would slowly kill everyone. Also, a high rate of CO2 production could overwhelm your ventilation. The rate of CO2 output from dry ice will depend on how cold the adjacent air is at the dry ice surface. In other words, you could probably kill yourself if you sat inside a car with rolled up windows in the hot summer, with a bunch of paper shopping bags full of dry ice chips touching warm beer bottles. With dry ice blocks instead of chips, slower gas production so less danger. Dry ice blocks not touching the bottles, even better. Dry ice blocks inside a styro-cooler not touching beers, the empty gap stays even colder, so even slower CO2 production and less danger. ---
**Author:** ![David42](https://avatars.discourse-cdn.com/v4/letter/d/5f9b8f/32.png) [@David42](https://boards.straightdope.com/u/David42)\ **Post date:** [July 17, 2011, 10:48pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/28 "2011-07-17T22:48:09Z")
> [@The\_Man\_In\_Black](#): > > I freeze plastic bottles of water all the time. Sealed bottles straight from the store. They don;t bust. I’ve had some break before but generally believe the plastic will stretch a bit. ---
**Author:** ![wbeaty](https://avatars.discourse-cdn.com/v4/letter/w/439d5e/32.png) [@wbeaty](https://boards.straightdope.com/u/wbeaty)\ **Post date:** [July 19, 2011, 2:19pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/29 "2011-07-19T14:19:18Z")
> [@brossa](#): > > So, if you want to keep your beer supercold for a short period of time, use frozen brine. If you want to keep it at not-quite-so-cold temperature for a longer period of time, use freshwater ice. Note that the freezing point of beer itself is about -2 or -3º C, and keeping it colder than that is just asking for slushy beer trouble. But also the freezing temp will rise when you open the beer and the CO2 comes out of solution. So you roll your eyes up, circle your hand over the bottle and scream “ANCIENT GODS OF ICE AND THUNDER HEAR ME” then pop the bottlecap. The beer turns to slush before your eyes. A wave of “slush-ification” passes through the bottle. More obvious with non-brown bottles. (Stolen from an Alan Moore comic episode w/Jack B. Quick, supergenius kid [Tomorrow Stories - Wikipedia](http://en.wikipedia.org/wiki/Jack_B._Quick)) ---
**Author:** ![IvoryTowerDenizen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ivorytowerdenizen/32/17937_2.png) [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)\ **Post date:** [July 19, 2011, 2:21pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/30 "2011-07-19T14:21:26Z")
> [@Ferret\_Herder](#): > > Dude, leave some headspace in the bottles. Problem solved. Put the bottles in zipper bags. If the bottles leak the water is contained. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [July 19, 2011, 2:56pm UTC](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945/31 "2011-07-19T14:56:44Z")
> [@TriPolar](#): > > … a solid bodied cooler will be relatively inefficient. The best way to get cooler efficiency is to remove the air space inside. If that’s not done with loose ice or tightly packing it with whatever the hell he’s keeping in there, a soft-sided cooler will be more efficient, and less likely to leak, because the ones I’ve seen have no drain hole pluggy thing that he’s missing. Either I’m not understanding this, or I completely disagree. A bunch of empty space inside a hard-sided cooler will not make it absorb heat any faster. For the same amount of ice, and the same insulation, a hard-sided cooler with some air space will not warm up any faster than a soft-sided cooler with no air space. And of course, hard-sided coolers are almost always better insulated than soft ones, so in reality, you’re going to be better off with the hard-sided, better insulated cooler. Now, obviously, if you fill up the air spaces inside the cooler with even more ice, everything stays cool longer, because there’s more ice to soak up the heat, so in the sense of losing opportunity, leaving air space is bad, but you’re not losing any efficiency (in the sense of cooling per amount of ice) by having air spaces inside the cooler. Anyway, to SupesKapow, in this case, salt won’t help. Chances are, there’s enough space in an unopened water bottle that it will freeze without bursting. But you could easily test a couple ahead of time by freezing them and seeing what happens. If the test bottles do rupture, then just open each bottle, pour out a little bit, then screw the cap back on tight and freeze. Voila, water-tight ice units. Put as many as you can in the cooler, just so you have as much cold units as possible, but don’t worry about packing the spaces between bottles with anything. [Previous page](https://boards.straightdope.com/t/science-officer-report-to-the-bridge-question-about-freezing-water/588945.md?page=1)