You’ve seen this in action, even if you didn’t realize it. That bag of rock salt you dump on your icy sidewalk? It’s not melting the ice by magic. It’s creating a tiny puddle of saltwater that stays liquid down to about 15°F (-9°C). But here’s the funny part: if it’s colder than that, your salt is just a sad, crunchy topping. You’re basically sprinkling seasoning on a frozen sidewalk—it won’t help.
PPT - Physical Oceanography PowerPoint Presentation, free download - ID
And then there’s cooking pasta. You salt the water because it makes the pasta taste less like cardboard, but there’s a bonus. The salty water has a slightly lower freezing point, so if you’re boiling pasta in a blizzard on a camping stove, that’s one less thing to worry about—your water won’t freeze as you’re draining it.
The Ocean’s Secret Sauce
This one fact is why marine life doesn’t get flash-frozen every winter. The ocean is a giant, salty soup that stays liquid in most coastal areas. If it froze solid, all the fish would be popsicles. Instead, sea ice is mostly fresh ice. When saltwater freezes, the salt gets pushed out into the surrounding water, creating super-cold, super-salty brine that sinks.
This is why icebergs are basically glacial, fresh water. You could, in theory, chop off a chunk of an iceberg and make a martini with it—it’s the purest water you’ll ever drink. Just don’t try that with the slush from the bottom of your driveway. That’s just dirty, salty sadness.
Table Salt Water Freezing Point at Paul Nichols blog
