The Physics of Boiling
Why do chefs add a pinch of salt to a pot of boiling water? While many think it's to make the water boil faster, science says the exact opposite: adding salt physically forces the water to boil at a higher temperature. This is known as Boiling Point Elevation.
Colligative Properties
Boiling Point Elevation is a Colligative Property. This means the effect does not care about what the chemical is (salt, sugar, or antifreeze); it only cares about how many particles are dissolved in the water.
When you dissolve a solute into a solvent, the solute particles physically get in the way of the solvent molecules, preventing them from easily escaping into the air as a gas. Because it's harder for them to escape, you have to apply more heat (a higher temperature) to force them to boil.
The Elevation Formula
The Van't Hoff Factor ($i$)
This is the most critical part of the calculation. It represents how many physical pieces the molecule breaks into when dissolved:
- Sugar (C12H22O11): Does not break apart. $i = 1$.
- Table Salt (NaCl): Breaks into one Na+ and one Cl-. $i = 2$.
- Calcium Chloride (CaCl2): Breaks into one Ca2+ and two Cl-. $i = 3$.