Does salt make ice melt faster?

Answer 1

Salt causes ice to melt faster because it lowers the freezing point of ice, which means it has to be colder than 0o Celsius for the ice to remain frozen. However, it is not only salt that causes ice to melt faster. Adding anything which will dissolve in water (for example, sugar or baking soda) would also make ice melt faster. This is because when water contains impurities, its vapor pressure is lower, and so it freezes at a lower temperature and boils at a higher temperature.

Answer 2

Yes because

• Molecules on the surface of the ice escape into the water (melting), and
• molecules of water are captured on the surface of the ice (freezing).

When the rate of freezing is the same as the rate of melting, the amount of ice and the amount of water won't change on average (although there are short-term fluctuations at the surface of the ice). The ice and water are said to be in dynamic equilibrium with each other. The balance between freezing and melting can be maintained at 0°C, the melting point of water, unless conditions change in a way that favors one of the processes over the other. The balance between freezing and melting processes can easily be upset. If the ice/water mixture is cooled, the molecules move slower. The slower-moving molecules are more easily captured by the ice, and freezing occurs at a greater rate than melting. You can see a demonstration of this by clicking on the temperature in the animation and setting it to a lower value (say, -10).

Conversely, heating the mixture makes the molecules move faster on average, and melting is favored. Reset the animation and then enter a higher value for the temperature (say 10) and watch what happens.

Adding salt to the system will also disrupt the equilibrium. Consider replacing some of the water molecules with molecules of some other substance. The foreign molecules dissolve in the water, but do not pack easily into the array of molecules in the solid. Try hitting the "Add Solute" button in the animation above. Notice that there are fewer water molecules on the liquid side because the some of the water has been replaced by salt. The total number of waters captured by the ice per second goes down, so the rate of freezing goes down. The rate of melting is unchanged by the presence of the foreign material, so melting occurs faster than freezing.

That's why salt melts ice.

To re-establish equilibrium, you must cool the ice-saltwater mixture to below the usual melting point of water. For example, the freezing point of a 1 M NaCl solution is roughly -3.4°C. Solutions will always have such a freezing point depression. The higher the concentration of salt, the greater the freezing point depression [1].

But won't any foreign substance cause a freezing point depression, according to this model? Yes! For every mole of foreign particles dissolved in a kilogram of water, the freezing point goes down by roughly 1.7-1.9°C. Sugar, alcohol, or other salts will also lower the freezing point and melt the ice. Salt is used on roads and walkways because it is inexpensive and readily available.

It is important to realize that freezing point depression occurs because the concentration of water molecules in a solution is less than the concentration in pure water. The nature of the solute doesn't matter. One might expect from the diagram above that solutes with large molecules are better at blocking water molecules travelling towards the surface of the ice. The hypothesis that solutes with large molecules cause a larger freezing point depression than those with smaller molecules is not in accord with experimental data! The misconception arises because the diagram can't be drawn to scale; the size of the molecules is very small compared to the distance between them. As ice begins to freeze out of the salt water, the fraction of water in the solution becomes lower and the freezing point drops further. This does not continue indefinitely, because eventually the solution will become saturated with salt. The lowest temperature possible for liquid salt solution is -21.1°C. At that temperature, the salt begins to crystallize out of solution (as NaCl·2 H2O), along with the ice, until the solution completely freezes. The frozen solution is a mixture of separate NaCl·2H2O crystals and ice crystals, nota homogeneous mixture of salt and water. This heterogeneous mixture is called a eutectic mixture.

Answer 3

Faster. Salt interferes with the process of freezing, by breaking up the molecules. However, ice must already be at least a little bit coated with water (partially melted) in order for salt to have a melting effect.

Answer 4

Salt lowers the freezing/melting point of water, so in both cases the idea is to take advantage of thelower melting point.

Ice forms when the temperature of water reaches 32 degrees Fahrenheit (0 degrees Celsius). When you add salt, that temperature drops: A 10-percent salt solution freezes at 20 F (-6 C), and a 20-percent solution freezes at 2 F (-16 C). On a roadway, this means that if you sprinkle salt on the ice, you can melt it. The salt dissolves into the liquid water in the ice and lowers its freezing point.

Answer 5

Salt makes ice melt faster because it makes the water's melting point become lower. For example pure water normally freezes (and melts) at 0°C (or 32°F), where as water with a high salinity (lots of salt) will freeze at temperatures as low as -20°C (depending on the salinity level.) And simply put, the reason that salt affects the rate of freezing or melting is because NaCl (salt) is a different substance from water (H2O) and both have two different chemical properties. The salt molecules inhibit the hydrogen and oxygen particles from coming together and forming ice. It more or less creates a new solution with a lower freezing (and melting) point. This is why salt is useful for keeping roads and sidewalks from getting icey.

Answer 6

Yes, salt speeds up the melting process of ice by lowering the freezing point of water. When salt is added to ice, the salt disrupts the balance between ice crystals and liquid water, causing the ice to melt at a lower temperature than it normally would.

Answer 7

yes its lowers the melting point of the ice and so causing it to melt.

Answer 8

yes salt melts ice faster.

Answer 9

yes much faster