Have you ever wondered why you always see chefs cooking pasta in salted water? Some people say it’s to season the pasta, which is true. However, it’s also that salted water boils at a higher temperature than unsalted water, which means that the pasta will cook faster.
Plain, unsalted water boils at 100 degrees Celsius (at sea level, anyway). When you add salt, you interrupt the interactions between the water molecules and it requires more energy (heat) to excite the water into its gas phase (to boil). It’s like being at a party with all your closest friends (you’re all water molecules), and having a group of strangers crash the party (they’re the salt molecules). It’ll take you extra energy to find your friends, right? And it’ll take you longer to find your friends, too.
As a result of interrupting these molecular interactions, salted water boils at a higher temperature. Exactly how much higher will depend on how much salt you’ve added.
But wait. If it takes longer for salt water to boil, isn’t that actually increasing the cooking time?
Well, yes and no. It will take longer for your pot of salted water to boil, but since it boils at a higher temperature, your pasta will cook faster. Generally speaking, the time you save by cooking pasta at a higher temperature more than makes up for the extra time you spend boiling salted water.