Boiling point elevation.?

Question

Ok, so I was doing the typical boiling point elevation experiment by addind salt to water.

This is supposed to raise the boiling point.

However, I noticed no raise in boiling point.

I was using 2 pints of water, and 4 tablespoons of salt.

I dissolved the salt thoroughly.

It didn't do anything though.

If anything, it may have lowered the boiling point.

I was using Kosher salt, it's a flaky type of salt.

What I want to know is, what could've happened to not make the boiling point rise, and what are the EXACT (chemical / physical)differences between Kosher (flaky) salt, and the normal grainy salt.

The thermometer is accurate. Before I added salt, I tried boiling water alone, and it started to boil at 97 degrees C, which is precisely what is should boil at, since I'm at 5000 ft.

When I added salt, and dissolved it, and boiled it, the boiling point the first time was 91 degrees C. Then I added 2 tablespoons of salt, then 3, and then 4. Each time it started to boil at around 91.

Later someone told me that the thermometer should be vertical. I had the thermometer at an angle, but even so, it measured the temperature of water without salt correctly, so I don't think that mattered.

The only thing worth mentioning about the weather was that it was pretty windy.

Answer 1

Salt does raise boiling points. So I'm a little puzzled by your experiment. Perhaps you need to add the salt BEFORE you start boiling. Or is that what you did. Not clear.

Also it should not make any difference if it is Kosher or not. Salt is salt and no religion changes its chemical nature. The difference in the texture of salt is of no importance.

You might want to try using more salt in you experiment.

Potential sources of error:
1. Inaccurate measurement of temperature. How good is your thermometer?
2. Changes to atmospheric pressure between experiments. Did a storm or weather front pass over?
3. Inaccurate measurements of salt (use mass instead of volume).
4. Water may be hard water containing high parts per million of calcium salts already. Try distilled water instead of tap water.

Answer 2

Anything dissolved in water will raise the boiling point and lower the freezing point directly proportional to the amount of solute dissolved. The elevation can be very slight though so I would suggest using a more sensitive thermometer. Also I would not compare your result to 100 degrees celsius because the BP of water will differ slightly at different elevations. I would measure the BP of water without the salt and then with the salt and you should see a difference.

The difference between Kosher salt and table salt is that Kosher salt contains no additives (like iodine for example.) It will still raise the boiling point.

Answer 3

I don't know why it didn't change the boiling point but the only difference between table and kosher salts are the texture and table salt usually contains iodine.

Answer 4

Salt is composed of NaCl - Sodium and Chlorine. Sodium is a metal which conducts heat very quickly. The salt added to the water will allow the water to reach boiling point faster, not increase it's boiling temperature. (unless you pressurize it)

If you want to increase/decrease boiling temperature, you should go to a high or low altittude, or cook the water in a pressure cooker.

Answer 5

What probably happened to you is the "high school lab effect." Perfectly well-documented experiments just don't work for no good reason.

Answer 6

your experiment was flawed. even nonelectrolytes like sugar will raise the boiling point