Question

why is cold freshwater denser than warm salt water

Answer 1

Depends on what you define as "cold"
When the freshwater is at it most dense point (4 degrees C) it's more dense than hot salt water. Though it also depends on the salt concentration. When the salt concentration is higher than a certain point, it is more dense than cold freshwater.
So it's not a very correct question, you would need to clarify the temperature and salt concentration.

Answer 2

The above answer is partly wrong. Ice is less dense than water, and that can be proven when you see an ice cube float in a glass of water. But its a bit more complex than that.

Water is one of the few things in nature that expands when it freezes (changes state from a liquid to a solid). Water is at its maximum density at 4°C, and density decreases rapidly below that. Here are some examples of density relative to temperature:

0°C: 0.915 g/cc
4°C: 1.000 g/cc
40°C: 0.9832 g/cc
80°C: 0.9718 g/cc

See how the density goes down on either side of 4°C?

Salt water is denser than fresh water, provided the temperature is constant. Thats why its easier to float in ocean water than lake water. The higher the amount of salt in solution, the denser the water.

Hence warm fresh water is less dense than fresh water at 4°C, but you don't specify if "cool" means 4°C or 0°C. Therefore you'd have to specify the temperature, and then refer to water density charts.

Answer 3

Curtsy of Minefinder~ Thanks!

Answer 4

did you just copy that from some other answer site?

Answer 5

I quoted my source didn't I? Yes though.

Answer 6

Here's the site: http://answers.yahoo.com/question/index?qid=20100208144421AAroUTq

Answer 7

since it looks like you're disagreeing with my answer :P

Answer 8

I just use my resources lol

Answer 9

Im sorry about the temp., thats just the question i was given to answer, Thank you both so much for attempting to answer it though, ill do my best to explain that in my answer.

Answer 10

No Prob anytime!

Answer 11

Thanks Laters!

Answer 12

http://scuba.about.com/od/Theory/p/Buoyancy-In-Salt-Water-Vs-Fresh-Water.htm