What temperature does salt water freeze at?
The freezing temperature of salt water depends on how much salt you put in. Oceanographers define the “salinity” of water as the number of grams of salt per 1000 grams of water. (Since 1000 grams of water is almost exactly 1 liter, it’s also grams of salt per liter). Here’s a table which gives the freezing point of water at a number of different salinities: S(g/kg) 0 10 20 24.7 30 35 T(freezing) (C) 0 -0.5 -1.08 -1.33 -1.63 -1.91 Away from rivers and glaciers, the ocean has a salinity of about 35. The Atlantic is about 1 salinity units saltier than the Pacific. So ocean water freezes at about -1.91 degrees C. The results of your experiment are strange. Usually, fresh water freezes at 0 C. Did you make sure that your thermometer was completely surrounded by the ice? Don’t freeze the thermometer into the ice: ice expands when it freezes, and you could easily break the thermometer. Instead, take the ice out of the freezer, put it it a styrofoam cup, and let it melt, and put the temperatur
