By how much does the boiling point of water change when you add salt?

Question

Does this temperature change make any difference at all when cooking, or is it an old wives tale?

Answer 1

It increases by 0.513 degrees C per mole of solute per kilogram of water. A mole of NaCl is 58.5 grams, but because it fully ionizes, you do the numbers on half that amout (29.7 grams). Converting to cooking units, two tablespoons of salt per quart of water raises the boiling point about one degree C. In most cooking, the amount of salt added is much too small to make an appreciable difference in temperature -- it's done mostly for taste.
At higher altitudes, the reduced pressure makes a marked reduction in boiling point: at 5000 feet, it's down to 95 C.

Answer 2

Not exactly an old wives' tale, because the temperature does risel -- the addition of salt changes the molality of the water, raising the boiling point in direct proportion to how much salt is added. In cooking, however, the change in boiling temperature really isn't enough to make any difference; you might raise the boiling point by a degree or three, but it's still going to take 8-10 minutes to cook pasta. What you DO accomplish by salting the water until it's about like seawater is that you are essentially brining the pasta, so as it cooks, it gets seasoned throughout the noodles (the molecules of salt get carried into the interior of the pasta by the cooking water)

Answer 3

No, this is not an "old wives' tale" It is something called a colligative property of a solution. Adding salt (a solute) to water will affect the boiling point and freezing point of water. In my chemistry I classes we generally get a boiling point elevation of 4 degrees Celsius. This is dependent on how much salt is added to the water. That is why you boil your macaroni in salt water instead of plain water. The salt added to the water lets the water get hotter to cook the macaroni better.

Answer 4

It raises the boiling point up to 5 degrees Celsius. Since cooking is a chemical reaction (denaturation of proteins), 5 degrees can have quite an effect on the rate of reaction (5-10 times faster, depending on many factors).

Answer 5

It TOTALLY depends on the Molar concentration of salt IN the water. Salt is soluble in water without boiling the water, or heating it, and dissociates ---> NaOH- + HClO+. But, the more heat you add to the solution, the QUICKER it dissolves in the water.