I always wondered why the snow or ice melts when you put salt on it.?
613215
Simply put, the salt lowers the freezing point of water.\n\nHow does it do this?  From kinetic molecular theory, the temperature of an object is proportional to the random motion of the molecules of the object.  As water cools down the molecules move slower and stick closer together until the intermolecular forces are stong enough to lock the molecules into a crystal structure (overcome random motion) and water freezes.  The salt lowers these intermolecular forces by interacting with the water molecules: there is some salt-water interaction and thus less water-water interaction.  Thus, a lower temperature is required to lock in the crystal structure (lower melting point) and the ice melts.\n\nThis works to about -30 or -40 C IIRC.
408260
About -1.8 degrees C, due to the freezing point depression of the dissolved salt (that's why they salt roads in winter)
284203
Ice lowers the melting point of water, so it causes the ice to turn to liquid water and break up.  If it's *really* cold, this doesn't help.
392443
That is an interesting question.  What is snow made of?\nWater, right? Except it is water frozen in a special\nway, by accretion of little bits as the snowflake\ndrops through the atmosphere, so that snow is pretty\nrandom stuff, compared to ice which is also frozen\nwater, but which has all the water molecules nicely\nlined up which makes it transparent.  The randomness\nof snow means that when light strikes the snow it\ngets scattered in all directions, and all colors are\njumbled up, so when you look at snow all you see is\nthe jumble, which shows up as white light.  When\nit melts, it just turns into water (and usually\ndisappears into the ground) which does not have the\nkind of randomness snow has at the level of the\nwavelengths of visible light.  (Visible light\nhas wavelengths much longer than the size of molecules).\nSo, the "white" did not really exist on its own -\nit was a property of the arrangement of the water molecules\nin snow, and disappears as soon as that arrangement is\nchanged.\n\nDoes this help?
650938
Saltwater WILL freeze. The temperature at which it freezes, however, depends on the amount of salt you add to the water. The more salt you add to the water, the lower the freezing point for the solution. You will reach a point when you have added so much salt that the freezing temperature will not decrease anymore.
776338
to spread salt early is a waste as cars and traffic will just throw it off the road.  salt is laid after snow or ice falls to melt the ice.\n\nmore and more its becoming common to salt brine the roads prior to a snow coming.  this is done with a mix of salt water and is laid on the ground normally in 5 straight lines.\n\nto a test of your own and you'll see why they salt it afterwards and not before with actual rock salt.\n\ntake a plate and put a layer of salt on it then lay an ice cube on it.  take another plate and lay an ice cube on it then salt over top of it.  which melts faster?
330025
it's frostbite. the water melting off the ice cube is because salt lowers the freezing point and so the water on your skin is very cold <32 so it freezes the skin. kinda like making ice cream except more painfull
35421
Ice will form on a surface that has water on it, if the surface is below freezing, or technically, can extract enough heat from the water to allow the water to fall to below freezing temperature.\n\nThis happens a lot when it has snowed, then there is a sunny or warm day, melting the snow to water because the ground temperature warms to above freezing.\n\nThen, at night, the ground will maintain the above freezing temperature for a while, but slowly cool off.\n\nA bridge has less 'mass' to maintain the warmer, higher, temperature, plus the air flowing above and below the bridge will cool the bridge faster, so it cools to below freezing faster. This causes bridges to frequently form ice more quickly than ground surfaces.\n\nUnder the right circumstances, the ice will form on the road as well. Just ask a busy auto body shop in winter.
55409
You can use sand but this does nothing to melt the ice. It merely makes it easier to get a little traction so you can drive over it. \n\nRecently, some areas use a liquid chemical de-icing solution (Calcium Magnesium acetate is one such solution) that gets sprayed directly to roads.  It is more expensive than salt.
726926
Salt... When applied to ice, the salt (NaCl) dissolves into the water creating a salt water mixture which has a lower freezing point than pure water.\n\n10% salt solution freezes at 20 F (-6 C)\n20% salt solution freezes at 2 F (-16 C)\n\nSalt becomes less effective at temperatures below 0F (-32 C).\n\nEnjoy!
684151
The freezing point of pure water is 0°C, but that melting point can be lowered by the adding any solvent such as a salt. Depending on the amount of salt the freezing temperature of a saline solution can range from below 0°C to -21.1°C. The frozen solution is a mixture of separate NaCl·2H2O crystals and ice crystals, not a homogeneous mixture of salt and water. This heterogeneous mixture is called a eutectic mixture. \nThe use of ordinary salt on sidewalks is effective because it requires a colder temperature to freeze water and it is a cheaper alternative to other solvents or methods of ice removal.
959702
If you make them the same concentration (say 1 molar of each) the salt water will have a lower freezing point, and so will need to be colder before it freezes.  Freezing point is affected by the concentration of particles dissolved in the solution.  Since salt forms two ions and sugar forms only single molecules, you have more particles in a salt water solution than you do in a sugar water solution.
78877
The "white" is caused because snow has a great many tiny interfaces, called "phase boundaries," where air (a gas phase) meets ice (a solid phase). Every time light encounters a phase transition, it is defracted. If you've ever looked at a stick submerged partially, you've seen this--a straight stick will look like it has a bend in it right at the water's surface. Well, with snow, the tiny ice crystals, and the many small bubbles in ice (water is a bent and polar molecule, so when it freezes, it expands, making small bubbles inside), and the places where individual ice crystals begin and end--all of this scatters light all around. This makes it so that a big bunch of snow will look white. If you look at a single snowflake under a microscope, though, you will see that the crystals individally are clear.\n\nWhen it melts, there is only one phase transition, right at the surface. The light is defracted a bit, but only once--it doesn't scatter light all around like snow does.\n\nBut it can! If you've ever seen a big fountain, where the water is splashing and tumbling about, it will also look white due to phase transition. Likewise, if you make a whole bunch of tiny bubbles under water, you can scatter light and make it look white.
883409
I will assume that "salt" is referring to sodium chloride, NaCl.  The solubility of NaCl increases with increasing temperature and decreases with decreasing temperature.\n\nSince you are starting with a saturated solution (meaning that it contains the MAXIMUM amount of NaCl at that temperature) and you are cooling the solution to 20oC from 60oC, the cooler solution will not be able to keep the NaCl dissolved and you will observe small crystals of NaCl precipitating from the solution.
402321
I was told that it was becuase of the mountains.The ice or snow of mountains would melt into water,forming small rivers that turn into more and more bigger rivers{or something like that} that turn into oceans."Where does the snow of a mountain or ice of a mountain come from?",you might ask.That I dont know.
980326
this was answered right here in Yahoo Answrs about 3 months ago:\n\n\n The river water keeps moving .This shows that there is no way of settlement of any minerals-this is the reason why the river wateris not salty.\n\n \nThe salinity of the ocean is caused by high mineral content. When water evaporates it leaves behind all of sediments and becomes pure water. When it falls as rain or snow it remains in this pure state. As it travel through rivers it picks up sediments. Most of the sediments remain in solid form and are pushed along by the river. However, salt dissolves into the water. When the water reaches the ocean, the salt deposit go as well. Over thousands and millions of years, the oceans have developed a high salt content. It's the same reason that lakes that have no outlet, such as the Great Salt Lake or the Dead Sea, become salty. \n\nAs a result of global warming, though, more fresh water is entering the ocean and its salinity levels are dropping. This can have significant environmental effects over time.
348819
fresh water\nany substance in water increases boiling temp\nthe particles of this substance "get in the way" of the water's gas molecules and makes it "more difficult" for the water to evaporate.\nso really, the myth that adding salt to water when making pasta makes it boil faster it enitrely wrong\nit actually makes it longer, but not by much time (a few extra mins)\nsimilarly, This is why we salt our roads\n the salt dissolves the ice and doesn't let it freeze again because it decreases freezing pt by, again, "getting in the way" of the water forming its 6-sided ring (solid state)\na lower temp (slow down the molucles EVEN MORE) is needed to freeze it