Why isn't 0°F the lowest possible temperature for a salt/ice/water mixture?

Answer 1

Ice requires a crystalline lattice structure. The salt ions (Na+ and Cl-) physically interfere with the formation of that lattice structure by standing in the way of water molecules. A lower temperature is therefore necessary to form ice and so water that contains ionic salt can drop to lower temperatures before forming ice. The same general effect applies to boiling water. Because the salt prevents molecules from escaping into the atmosphere as gas, the boiling point is raised.

Note: I assume you meant 0 degrees Celsius. The Fahrenheit scale is somewhat different, since water freezes at 32 degrees Fahrenheit. But don't let these numbers cause you to believe something different is going on in the salt/water/ice mixture. The Celsius scale is set such that water freezes at 0 degrees (absent salt). This doesn't mean that at 0 Celsius and below there is no temperature or energy. Just the same, below 0 degrees Fahrenheit compounds still have energy and temperature. Scientists tend to use another scale which more accurately depicts true temperature, which is the Kelvin scale. In the Kelvin scale, absolute zero- the temperature at which all molecules and atoms stop moving- is really 0. But 0 Kelvin is much lower than either 0 Celsius or 0 Fahrenheit. To convert from Celsius to Kelvin, just add 273 degrees (or subtract 273 from Kelvin to Celsius). So 0 Celsius is actually 273 degrees Kelvin.

In any case, if you were looking for an answer that has to do with the chemical properties of the salt/ice/water mixture, and why, for example, salt tends to lower the freezing point (or raises the boiling point), my first answer is right. Any solute you add to a solvent will change the colligative properties of the solvent. It interferes with the organization of water molecules such that they have a harder time aligning into a crystalline ice pattern, and therefore a lower temperature is required for ice to form. Note also that whenever you have an ice/water mixture, the entire mixture maintains the same temperature until all of the water has turned to ice. That is, in pure water that contains ice, the water will stay at 0 degrees Celsius until all the water has turned to ice, and then the ice will gradually drop in temperature. The salt just lowers that freezing point, but the same applies, just that the salt/water/ice mixture remains at that lower freezing point until all water as frozen, then it drops further in temperature.

Answer 2

No. Ice/water mixture should be at 32°F or 0°C, but if you add salt, the freezing point would drop. The more salt, the lower the freezing point below 32°F or 0°C.

Answer 3

It is due to that is called collegative (sp) properties. Bascilly the melting point of a liquid is lower by a set C by each time a mole of substance is dissolved in it.

As salt is highy dissoluable in water it will lower the natural freezing point of water by x degrees and hence 0 C is not the lowest temperature for it.

Answer 4

Because the Fahrenheit temperature scale is completely arbitrary, and has nothing to do with nature itself. Also, altitude changes things. I don't know about a salt/ice/water mix, but pure water boils at 100 deg. C at sea level, but it boils at 94 deg. C in the Rocky Mountains. Depending on where you live, that might have something to do with it.

Answer 5

When Fahrenheit created his temperature scale, he used a specific amount of salt in water and then determined its freezing point. This temperature was set as 0F. Had he used a different amount of salt the freezing point of his solution would have been different. If you create a solution with more salt dissolved in the water, then it will lower the freezing point to below 0F.

Answer 6

Thats just the way the Farenheight system is set up.

It is not uncommon in many parts of the world for the temperature to drop below 0ºF.

Also, I'm impressed that you actually used the symbol for degrees.

Answer 7

Then it'd be 0 Kelvin.

Unless you mean when water freezes at sea level, that'd be 0 Celcius.

Answer 8

Why not have 0 degrees Kelvin be where things don't move... and we could live at like 290 degrees K?

Answer 9

??

The scientific measurement for temperature is in Kelvin.

Freezing Point and Boiling Point in Kelvin is 273.15k and 373.15k

In Celsius it's 0c and 100c

Fareheit it's 32F and 212F

Answer 10

Because the molecules still contain energy which can be removed.