How does salt in boiling water make food cook faster?
Well it has to do with solutions. When you dissolve something in a liquid, particularly water, the vapor pressure decreases. Now for boiling to occur, the vapor pressure in the liquid must be equal to atmospheric pressure. Usually, water has a vapor pressure lower than atm. pressure, so to get it equal, you heat it, which raises vapor pressure. Once the vapor pressure becomes as high as the atm. pressure, boiling occurs! (boiling is simply a rapid phase change to gas) Back to the salt water: when you dissolved the salt in water, like any solute, it makes the vapor pressure decrease. Now that the vapor pressure is lower than pure water’s vapor pressure, more heat must be added before it equals atmospheric pressure. So it takes longer for it to boil. So the boiling point increases when the initial vapor pressure decreases. In your case, the dissolved salt caused the drop in vapor pressure. So in essence, when you dissolve something, it drops vapor pressure, so more heat (and time) is req
