Weatherlawyer wrote:
Holly, in France wrote:

Question about how much salt it takes to lower the freezing point of
water. If one has a swimming pool with about 80 cubic metres of water,
and adds 18 25kg bags of salt (enough for the chlorination machine to
say 'enough is enough'), how much will the freezing point of the water
be affected?

Sea water is 37 grams per litre all you need to do is find out what
temp that freezes and you will know. I think it is about -2 degrees
Centigrade. But with that sort of concentration, the mechanics change
(you will need to watch that.)

Any ice that forms will increase the concentration of the rest of the
pool.
Yup
As will any evapouration.
Yup.
As it cools it gets denser and falls to the floor. All the cold water
will be at the bottom of the pond until the ice forms.
Nope. For pure water the maximum density is at 4 degC (the value will
be different for salt water). Once the water has cooled below this
temperature, the water will be cooler at the top and warmer at the
bottom