why do salt can melt ice?

Answer 1

I think that these answers are either too complex (although true), or too simple,and perhaps miss the point.

Water freezes because water molecules bond to each other. Toss some salt onto it, and the water molecules want to bond with the salt instead of each other. The salt literally "pulls" the ice apart.

If you want to get technical about it, H2O is a "polar" molecule that is slightly negative on one end, and slightly positive on the other. Salt is an ionic solid that splits into a negative ion and a positive ion upon contact with the water. The bond between Na+ and/or Cl- is stronger at certain temperatures than it is to other H2O molecules.

If you want a more accurate explanation than the one that I just gave you (I was being overly simplistic), try the website below:

Answer 2

Ice melts at 32 degrees F (at normal sea level pressure). Sprinkling salt on ice LOWERS ice's melting point, to let's say 25 degrees F. Thus, without salt, if the temperature is 29 degrees, water will freeze into ice. With salt sprinkled on the ice, and if the air temperature is 29 degrees F, the water will remain liquid.

Adding salt to water will also RAISE the boiling point of the water. Normally, water boils at 212 degrees F. Add some salt to the water, and suddenly, the water won't boil UNTIL it reaches a higher temperature, say, 220 degrees. That's why some cooks add salt to a boiling water pot - - - to raise the temperature of the water to a higher point, so the food will cook a little quicker, or at a hotter temperature.

Answer 3

Salt water has a lower freezing point than fresh water. So, if the temperature outside is lower than the freezing point of fresh water (32 degrees F), it is probably still above the freezing point of salt water, so the ice melts.

Answer 4

Freezing/melting point is a colligitive property meaning the concentration of solute (dissolved particles) affects the point of measure. Pure water freezes at 0 degrees C by forming a network of molecules referred to as a lattice and in the case specifically to water--ice. By having these salt particles in the solution physically prevent the lattice from forming as easily and hence needing a lower temperature to finally freeze.

Think about stacking plastic dixie cups, quite easy, now consider placing a rock on the back of each cup and stack them, they no longer fit together as well and in order to stay together there would need to be a little extra something to hold them together.

Answer 5

The salt disolves and forms a solution with the ice/water. The freezing point of the solution is lower than the freezing point of pure water.

Answer 6

It raises the freezing point of the water, so therefore it melts faster than it would normally. It also partially absorbs the water.

The same thing kinds happens when you add salt to water that you want to boil, it lowers the boiling point so the water boils faster.

Answer 7

Salt actually just reduce the freezing point of water, which in turn forms a 'freezing mixture' of salt & water at about -20C.

Answer 8

salt causes heat when mixed with water, the ehat melts the ice

Answer 9

salt lowers the freezing point of water. since salt water freezes at 0F and normal water freezes at 0C, the ice turns into really cold salt water.

Answer 10

Because salt raises the freezing point of water, requiring cold temps. for the water to freeze.