albertlee Posted June 14, 2004 Author Posted June 14, 2004 To enable the salt solution to reach the dynamic equilibrium' date=' where the number of freezing particles equals the number of frozen particles we must lower the temperature so that the particles attach to the ice molecules. When the particles/molecules equal each other the are said to have reached “dynamic equilibrium” The higher the molarity of salt the lower the freezing point. The solution (NaCl·2H2O) crystals and ice crystals. This heterogeneous is an eutectic mixture.[/quote'] dynamic equilibrium...Um... Is the subject of adding salt to ice a matter of physics? secondly, what are freezing and frozen particles? apreciate the responds in advance Albert
YT2095 Posted June 14, 2004 Posted June 14, 2004 I fry courgettes - much nicer Absolutely! cut thickly at an angle' date=' coated in Olive oil, Sea salt and black pepper then put onto a hot griddle pan! <Slurp> btw, anyone here ever make "Freezing Mix" in basic Chem? it`s just Ice, Plain house salt (NaCl) and a little water. it`ll get as low as -15c although -14.7 was the best we ever got in the Lab, non the less, it`s an appreciable drop in melting point! [edit'] if you REALLY want to cheat, replace the house salt (NaCl) with Ammonium Nitrate (NH4NO3), it`s a real "brass monkey" job!
wolfson Posted June 14, 2004 Posted June 14, 2004 Albertlee i have given you the answer so use books and learn the "dynamic equilibrium" in CHEMISTRY terms not Physics, why would i be talking about physics?
albertlee Posted June 14, 2004 Author Posted June 14, 2004 dynamic equilibrium...Um... Is the subject of adding salt to ice a matter of physics? secondly' date=' what are freezing and frozen particles? apreciate the responds in advance Albert[/quote'] Any body can explain to to that? Albert
YT2095 Posted June 14, 2004 Posted June 14, 2004 " freezing" is merely the act of a liquid becoming a solid (often in an organised fashion, Crystaline). this can occur in at a wide range of temperatures, from helium to tungsten, "Frozen" simply means Solid, nothing more fancy than that the iron metal in your chair is "Frozen" the soda pop or beer in your cup is not frozen
albertlee Posted June 14, 2004 Author Posted June 14, 2004 So, where does the heat go and how? Albert
wolfson Posted June 14, 2004 Posted June 14, 2004 On a side note, we had a competition in chemistry class to see who could get water the coldest with salt and ice. The coldest we got was close to -20C. (And a guy held his finger in there for one minute for a $5 bet, and had to be treated for frostbite...) Its supposed to be around 251.05K (-22.1oC)
YT2095 Posted June 14, 2004 Posted June 14, 2004 So' date=' where does the heat go and how? Albert[/quote'] lookup Entopy and Enthalpt, the molecular disasocsiation of some compounds requires energy (endothermic but not a reaction! exactly) ans so the "heat" goes into that anyway, I`m off, got lot`s of work to do, cyaz l8r )
swansont Posted June 14, 2004 Posted June 14, 2004 So' date=' where does the heat go and how? Albert[/quote'] Into the surroundings, whatever they happen to be, as long as it's colder.
apathy Posted June 14, 2004 Posted June 14, 2004 salt in a boiling pot of pasta is for taste and that's about it. actually, if you put too much salt in something that is boiling, mostly rice or oatmeal, it will take longer to cook or it will be hard and not yummy, because the salt "held on" to most of the water, not allowing it to diffuse into the carbohydrates in the starchy food
albertlee Posted June 14, 2004 Author Posted June 14, 2004 Albertlee i have given you the answer so use books and learn the "dynamic equilibrium" in CHEMISTRY terms not Physics, why would i be talking about physics? Well, Wolfson, the term "dynamic equilibrium" in my science encyclopedia means about the balance of center of gravitity...... and dynamic means "moving".... I cant find anything on Chemistry about it... Can you or any one tell me about what is dynamic equilibrium or the resources about it? Apreciate in advance Albert
Cap'n Refsmmat Posted June 14, 2004 Posted June 14, 2004 On a side note' date=' we had a competition in chemistry class to see who could get water the coldest with salt and ice. The coldest we got was close to -20C.(And a guy held his finger in there for one minute for a $5 bet, and had to be treated for frostbite...)[/quote'] Yet another side note is that if you mix wood shavings with water and freeze it, you get pykrete, a strong substance with the density of concrete. Google for Pykrete
albertlee Posted June 15, 2004 Author Posted June 15, 2004 Sorry for asking again....but I still need to know this in order to understand..... Can you or any one tell me about what is dynamic equilibrium or the resources about it? Refer to my previous message Apreciating the responds Albert
albertlee Posted June 15, 2004 Author Posted June 15, 2004 Any body has an idea refer to my previous message? Sorry for this irritable post Albert
apathy Posted June 15, 2004 Posted June 15, 2004 OK, so the term "dynamic equilibrium" is as general as it sounds. Take the word "equilibrium" and look it up, then take the word "dynamic" and look it up, then modify the word equilibrium with the word dynamic and you now have the definition. You can apply that definition to whatever context it applies to. If you want to talk about gravity, a chemical reaction, the stock market, global politics, whatever.
albertlee Posted June 16, 2004 Author Posted June 16, 2004 Which part of chemistry is this very likely to be? I want to look up more about this in my chemistry encyclopedia. Any idea? Albert
wolfson Posted June 16, 2004 Posted June 16, 2004 http://search.yahoo.com/search?p=chemical+dynamic+equilibrium&ei=UTF-8&fr=fp-tab-web-t&cop=mss&tab= look at how many there is READ them and LEARN.
albertlee Posted June 16, 2004 Author Posted June 16, 2004 To enable the salt solution to reach the dynamic equilibrium' date=' where the number of freezing particles equals the number of frozen particles we must lower the temperature so that the particles attach to the ice molecules. When the particles/molecules equal each other the are said to have reached “dynamic equilibrium” The higher the molarity of salt the lower the freezing point. The solution (NaCl·2H2O) crystals and ice crystals. This heterogeneous is an eutectic mixture.[/quote'] Thx Wolfson for the link.... Now I realize......but if it is in a equilibrium, then at what temperature would it do opposite? Secondly, According to Wolfson's quote, Does the "attach" mean "to dissolve"? Albert
wolfson Posted June 16, 2004 Posted June 16, 2004 Well the new solution reaches its max/perfect equilibrium at -22oC, so any where above that it would not be totally in the equilibrium. So if the temperature outside is -5 the ice would melt, but it is was -24 outside it would not melt. Attach is basicly reaching the equilibrium, so yes melt/dissolve before the max -22oC.
albertlee Posted June 16, 2004 Author Posted June 16, 2004 then so do any substance that can dissolve in water would lower the freezing point of ice? Albert
aommaster Posted June 16, 2004 Posted June 16, 2004 That was answered in post #8 by swansont: As far as I know, yes. It's simply a function of the molar concentration of the solute. So pure water freezes at the nominal temperature of 0 C, and everything else is a some point colder than that.
JLB Posted January 15, 2005 Posted January 15, 2005 Does anyone know if water is the only element to freeze from the top down? Is that because the air is cold and makes it freeze that way?
swansont Posted January 15, 2005 Posted January 15, 2005 Does anyone know if water is the only element to freeze from the top down? Is that because the air is cold and makes it freeze that way? It's because water has its highest density at ~ 4 C, so that water sinks to the bottom, and the coldest water is at the top.
budullewraagh Posted January 15, 2005 Posted January 15, 2005 the only substances that share this property with water are bismuth, gallium, germanium and antimony
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