Saltwater has a much lower freezing point (the freezing point is the temperature where something freezes) than freshwater does. And the more salt there is in it, the lower the freezing point gets. So in order to know the exact temperature that it’s going to freeze, you have to know just how salty it is. For saltwater that’s as saturated as it can possibly get (i.e. there’s no way to dissolve any more salt in it no matter how hard you tried), the freezing point is -21.1 degrees Celsius. This is when the saltwater is 23.3% salt (by weight). Why ?
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Also checkout Salt and the boiling point of water.
Re: How does adding Salt to water affect its freezing degree and why?‘
Date: Mon Mar 16 06:23:54 1998
Posted By: Kathy Counter Benison, grad student, Geology, University of Kansas
Area of science: Chemistry
ID: 889727519.Ch
Message:
Salt lowers the temperature at which water freezes and melts. Pure water,
H2O, freezes (and melts) at 0°C (32°F). But the more “salt” (any elements
or compounds carried by the water in solution, such as Na (sodium), Ca
(calcium), Cl (chloride), and SO4 (sulfate)) in water, the lower its
freezing point. For example, seawater, which has approximately 3500 parts
per million “salt” (including Na, Ca, Cl, SO4, Mg, K, and CO3), will freeze
(and melt) at -2.2°C. A water with extreme salinity such as very salty
lake waters at Death Valley, California (approximately 300,000 parts per
million “salt”) may freeze and melt at temperatures as low as -20 – -30°C!
Because salt lowers the freezing point depression, it is added to icy roads
in order to melt the ice.The reason why salt lowers the freezing temperature of water is a bit more
difficult to explain without discussing more complex chemistry. Basically,
pure water, H2O, is a different substance than salt water, such as NaCl-
H2O. As different substances, they have different chemical properties.
Salt “gets in the way” of the interactions between H and O, making it
harder for the H and O to bond as ice.
You can do very simple processes in the lab or classroom illustrating this
principle. Fill two containers with water and put table salt in only one
container of water. Put both containers somewhere cold (in the freezer or
even outside over night). See what heppens!
Kathy Benison
Asst. Professor of Geology
Central Michigan University
Mt. Pleasant, MI
hi i am going to ask a question
does the amount of salt affect the freezing point of ice??
yes it does affect the freezing point of ice.
i think you are asking about freezing point of salt water, right ? answer is yes, freezing gets lower when there is more salt.
i don`t really know about that but good job
I am ten years old and I hate you. You stink pee you!
i wanted to know wat the BOILING point for salt water was not the FREEZING point. ta xoxo
the answer is something thats the answer.lol actually the answer is 100 degrees celcus nd 212 degress farenheit
Does water boil faster if you put salt in the water?
Yes and no. If you look at how fast water boils when you add a small amount of salt to it, such as when cooking your noodles, the change is insignificant between pure water and the salted water. However, if you take two identical pots and add one gallon of pure water to one pot and one gallon of 20 percent salt water to the other and heat the two pots on identical stoves, the pot containing the salt water will come to a boil first. Surprised?
To truly answer the question, one must look at what it takes to boil a container of water.
The time it takes a bucket of liquid to boil is controlled by essentially three things. The first is how much heat or energy you put into the bucket. The second is how fast the temperature rises in response to the heat input (the liquid’s heat capacity), and the third is the boiling point of the liquid. Assuming that we can control our stoves and add the same amount of energy to each pot, this variable becomes insignificant.
The boiling point of water does rise if you add salt to it, but only by about 2°C (4°F) to 102°C (216°F). Remember, water boils at 100°C (212°F). This is an insignificant change for adding such a large amount of salt. For you science nerds out there, the boiling point increase is calculated using the “ebullioscopic” constant of water. This leads us to the important variable, how fast water or salt water heats up, or the solution’s heat capacity.
The heat capacity of water is very high. What this means is that it takes a lot of energy to raise the temperature of water 1°C; in fact, the calorie is defined as the amount of energy that it takes to heat one gram of water to 1°C. Not to digress, but the high heat capacity of water is good, especially if you live on a planet where two-thirds of the surface is covered by water – it helps regulate the global temperature.
Now back to the question. If you look at the heat capacity of salt water, you will find that it is less than pure water. In other words, it takes less energy to raise the temperature of the salt water 1°C than pure water. This means that the salt water heats up faster and eventually gets to its boiling point first.
Why does salt water have a lower heat capacity? If you look at 100 grams of pure water, it contains 100 grams of water, but 100 grams of 20 percent salt water only contains 80 grams of water. The other 20 grams is the dissolved salt. The heat capacity of dissolved salt is almost zero when compared to the high heat capacity of water. This means that the heat capacity of a 20-percent salt solution is 80 percent that of pure water. Twenty percent salt water will heat up almost 25 percent faster than pure water and will win the speed race to the boiling point.
Please note that this will not hold true if you take two identical pots containing one gallon of water each and add the salt to one pot because then the volume of liquid in the salted pot will be greater than the one gallon starting point.
well i think that this is possible and i have to do an experiment so this is what i wanted to do
i am doing an expiriment too but i am finding out about frezzing saltwater
how much does the amount of water in salt effect the speed of the water freezing?
hi davon,
as long as there is salt in water, the freezing point lowers, more salt in water (or less amount of water in salt) translates to even lower freezing point.
what is the difference in time between the freezing point of pure water and the freezing point of salty wate depending on how many tasp of salt there is in eac cup of water?
this is mint i use this all f the time to loose weight and it works i did weigh 119 stone now i weigh 116
I’m Doing a experiment about different amounts of salt affecting how long it takes to freeze water at 70 Degrees farenheit can you guys tell me how long does it take to freeze saltwater from the ocean????
So does it mean that the more salt there is in the water, the slower it freezes?
hi safah masoud,
I don’t quite understand your question. I guess you are asking the time difference in freezing pure water and salt water. Well, you have to try and experiment it yourself.
Hi Chargers#21,
Experiment it and you should know the answer.
Hi Shazzy,
Yep, it should take longer to freeze because salt water has a lower freezing point.
[...] Freezing point of salt water The Official MartinZ Blog Does water boil faster if you put salt in the water? Yes and no. If you look at how fast water [...]
very informative site
About how much time should it tale for water with 5tsp of salt to freeze? I think something is wrong with my experiment.
awesomeness! it helped me with my science fair project
If you freeze saltwater, will that remove the salt?
omg this totally helped me with my science fair report
yayyy!
so in general, does water boil faster with pure ocean salt water?
This is very informative article thank you
But one question
What is the maximum amount of salt you should add if you were to test the levels of boiling?