why does fresh water freeze faster than salt water?
916940
Salt water has a lower freezing point.
288935
Fresh water freezes when the temperature of the water is 32*F and the pressure is normal atmospheric pressure. And then, if there is a heat loss for that fresh water, then it would freeze at lower pressures also. \nIf ice is at 32*F and there is a heat gain, it would melt at 32*F. Also, if at 32*F with no heat flow there is higher pressure, then ice would melt. (eg skiing. If you put your pressure on the skis, the ice/snow melts and becomes water so that you can ski)
782187
When salt (NaCl) is absorbed into water (H2O) A new molecule is formed (NaH2ClO). When this new molecule is frozen, the crystalline structure is much stronger than that of regular water. This is why icebergs sink ships and ice cubes can be crushed by your refrigerator.
290700
(m)\n\nEveryone who has been to the beach knows that seawater is salty. Everyone also knows that fresh water in rain, rivers, and even ice is not salty. Why are some of Earth’s waters salty and others not? There are two clues that give us the answer. First, “fresh” water is not entirely free of dissolved salt. Even rainwater has traces of substances dissolved in it that were picked up during passage through the atmosphere. Much of this material that “washes out” of the atmosphere today is pollution, but there are also natural substances present.\n\nAs rainwater passes through soil and percolates through rocks, it dissolves some of the minerals, a process called weathering. This is the water we drink, and of course, we cannot taste the salt because its concentration is too low. Eventually, this water with its small load of dissolved minerals or salts reaches a stream and flows into lakes and the ocean. The annual addition of dissolved salts by rivers is only a tiny fraction of the total salt in the ocean. The dissolved salts carried by all the world’s rivers would equal the salt in the ocean in about 200 to 300 million years.\n\nA second clue to how the sea became salty is the presence of salt lakes such as the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than seawater. Why are these lakes salty while most of the world’s lakes are not? Lakes are temporary storage areas for water. Rivers and streams bring water to the lakes, and other rivers carry water out of lakes. Thus, lakes are really only wide depressions in a river channel that have filled with water. Water flows in one end and out the other. \n\nThe Great Salt Lake, Dead Sea, and other salt lakes have no outlets. All the water that flows into these lakes escapes only by evaporation. When water evaporates, the dissolved salts are left behind. So a few lakes are salty because rivers carried salts to the lakes, the water in the lakes evaporated and the salts were left behind. After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels. The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean. Because of the huge volume of the oceans, hundreds of millions of years of river input were required for the salt content to build to its present level. \n\nRivers are not the only source of dissolved salts. About twenty years ago, features on the crest of oceanic ridges were discovered that modified our view on how the sea became salty. These features, known as hydrothermal vents, represent places on the ocean floor where sea water that has seeped into the rocks of the oceanic crust, has become hotter, and has dissolved some of the minerals from the crust, now flows back into the ocean. With the hot water comes a large complement of dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate that the entire volume of the oceans could seep through the oceanic crust in about 10 million years. Thus, this process has a very important effect on salinity. The reactions between seawater and oceanic basalt, the rock of ocean crust, are not one-way, however; some of the dissolved salts react with the rock and are removed from the water.\n\nA final process that provides salts to the oceans is submarine volcanism, the eruption of volcanoes under water. This is similar to the previous process in that seawater is reacting with hot rock and dissolving some of the mineral constituents.\n\nWill the oceans continue to become saltier? Not likely. In fact the sea has had about the same salt content for many hundred of millions if not billions of years. The salt content has reached a steady state. Dissolved salts are being removed from seawater to form new minerals at the bottom of the ocean as fast as rivers and hydrothermal proce
419356
I will take a stab at it.  I am guessing it is because water has more degrees of freedom.  In the liquid there is also rotational degrees of freedom to absorb energy that the solid ice does not have.\n\nTo Neil, the formulas are for heat capacity and have nothing to do with the way something is heated, only the amount of energy that it takes.\n\nNor does it have anything to do with Newton's law of cooling.
844743
adding salt to water increases the boiling point and lowers the freezing point, so it definitely wont be the salt water. (on another note, that's why some people add salt to the water when making pasta- the water will begin to boil at a higher temperature, so when the person adds the pasta to the water it cooks faster).\n\nsugar water would have a less dramatic effect than salt water, but plain water itself would freeze the fastest.
162986
We typed "how does salt melt ice" into the Yahoo! Search box and were soon traveling the well-worn path to How Stuff Works. \nThere we learned that the answer has to do with melting points. Most people know that water freezes at a temperature of 32°Fahrenheit (0°Celsius). Salt dissolves fairly rapidly in ice, lowering its freezing point in an effect known as freezing point depression, and melting it in the process. \n\nBut what's going on at the molecular level? Basically, salt molecules are bonding with water molecules, making it more difficult for ice to form. The result is a solution with a lower freezing temperature. For example, a 10% salt solution freezes at 20°F (-6°C), while a 20% salt solution freezes at 2°F (-16°C). \n\nYou've also probably noticed the effect of salt water on freezing points if you've tried to make ice cream or if you've wondered why the ocean doesn't freeze at the same time as bodies of fresh water, such as rivers, lakes, and ponds.
125319
The ice water will cool quicker.  The reason being, that the water will cover the entire surface area that you are trying to cool.  \n\nThat being said, it also won't last as long because it also has more surface area for the cooling to escape.
899981
This is what happens if you start freezing a glass of sea water: it will start to freeze at a lower temperature than fresh water (around -4 C, but variable depending on the salinity you start with). \nImportant, the salinity of the ice formed is almost pure water (it is not salty). Some salty water may be trapped on the ice though, but the ice itself is fresh water. If you keep lowering the temperature, more ice will form and the remaining salty water gets even saltier. This process will continues until an eutectic is reached and then you will have a fast crystallization of ice, a mineral called hydrohalite. This eutectic is about -21 C, but depends on other components, like Mg, Ca that are also abundant in the composition of sea water.
12598
Because the water collects minerals from the floor of the ocean and so on and it isn't circulated or "refreshed" as a freshwater lake would be.  For instance, the Great Lakes are freshwater because they constantly drain out into the oceans.  The water is replenished all the time, not just sitting in one spot.  It doesn't give them time to collect the minerals to get salty.  If a lake, such as the Great Salt Lake in Utah, doesn't have this circulation (not sure what the scientific word is for it, but there is one), a place to drain so the water can be replenished, it becomes salty because it absorbs the minerals.
868477
water freezes at 32 degrees Fahrenheit, and 0 degrees Celsius\n\nthe colder the faster
260171
It isn't air! When water freezes all dissolved gases & other matter are not included!!! \n\nThe hydrogen bonds that form when water freezes creates an open structure. There is simply nothing in between those spaces.\n\nWe are talking about molecular structure, things at this level are so tiny that even thinking about what is in between is silly.\n\nIf there is anything between the spaces it is probably interstitial water molecules (those not hydrogen bonded inside the crystalline lattice structure - think of them as loose molecules of water).\n\nIce floats on water because it has expanded. That is all. Not because of what is in between the "spaces".\n\nSee, when you increase the surface area but have the same number of molecules present, you cause the object to become less dense. (it's less tightly packed...things that are tightly packed for their size are said to be more dense.)
199280
Salt causes the freezing point of water (and any other solvent for that matter) to be lowered. Thus, a salt solution freezes at a lower temperature than pure water. This phenomenon is called "freezing point depression." The extent to which the temperature is lowered is a function of the molality (moles of solute per kilogram of solution). That means that the more salt you add, the lower will be the freezing point.
75493
Salt lowers the freezing point of water, making the salt/ice combination colder than ice alone.  This makes the ice cream freezing process faster.
656503
It doesn't.  Ice melts more slowly on a colder surface because when ice melts it must draw heat from the surrounding environment, and when there is less heat available it takes longer.\n\n____________\nEdit: as a college science major, I can tell you it simply doesn't work that way.  However, there are a number of factors besides temperature that effect ice melting.  For example, if the piece of ice on the colder block was considerably thinner than the ice on the warmer block the one on the colder block might still melt faster.  In biology, we sometimes melt small amounts of liquid on ice because bad things happen if they get too warm, and two microliters of frozen liquid on ice generally melts faster than ten mililiters in warm (about 98˚F) water.\n\nAnother factor that effects melting point is solutes dissolved in the water before it was frozen.  Salt water freezes at a lower temperature, and consequently melts at a lower temperature, than pure water (that's why the salt the roads in the winter).  If there were a lot of salt dissolved in the piece of ice on the cold block, then depending on the temperatures of the two blocks, the one on the cold block might melt faster.\n\nIt's also possible that one or both pieces of ice weren't water at all.  There are plenty of clear liquids out there that melt at various temperatures.  A compound with a lower freezing point will tend to melt faster, possibly even at a lower temperature.\n\nAnother factor is the starting temperature of the ice.  In one of the biology labs at my school we have a freezer that's at -80˚C, and the normal ones at 4˚C.  If you take a piece of ice out of the -80˚C freezer and one out of the 4˚C freezer, they're both frozen, so they're both ice, but the one at -80 is a lot colder, and is going to take a lot longer to melt, even at a warmer temperature, because it has to warm back up to 0˚C before it can even start to melt.\n\nBut, of course, the obvious explanation is that either your teacher lied to you, or you lost track of which block was which at some point in the demo.
62870
Cold Water. - Most of the time. \nI have tried and tested this before (Tap Water). The hot water normaly takes about 10 minutes longer. When using Tempratures like 30 degrees and 70 degrees this will begin to vary and warm water might start freezing faster than cold water. \n\nWarm water can in fact sometimes freeze faster than Cold water but it very much depends on the conditions.\n\nWhat you are thinking of is the Mpemba effect. This could be due to a number of factors including but not limited to Evaporation (less water needed to be freezed), Dissolved Gasses and Convection.\n\nFor a lengthy but thorough explanation see the link below.\n(Very reliable references) \nhttp://math.ucr.edu/home/baez/physics/General/hot_water.html
178613
Water freezes faster.  All sodas contain acid which lower a liquid's freezing point.  The lower the freezing point, the longer it takes something to freeze.