Why is hot water often cloudy?

[Sublime54465]

recently i was washing some pots in the sink, and i noticed that the hot water came out undeniably more cloudy than the cold water. i tested it at a few differnt places around my house and around campus at my school, and it seems to be a recurring phenomenon. why is that? why is hot water cloudy, and cold water clear?

[Ringo]

The City of Tucson’s take:

Hot water will sometimes be cloudy due to the physics of heating and moving the water through a pressurized system. As water is heated, the gases dissolved in the water will escape. (That’s why most water heaters have a pressure release safety device.) As the hot water is released at the tap, the gases immediately begin to separate from it. The water will clear quickly.

I suppose you might also be seeing some mineral preciptates in suspension.

[Phlosphr]

IANA Scientist but if you take a pint glass fill it with said hot water, look very closely, the cloudy appearence is actually tiny bubbles. So one can only deduce the hotter the water the more oxygen it holds thus producing a cloudy appearence. The cooler the water the less energetic room for oxygen so it appears more clear.

OH GOD! some one come help me out that just doesn’t sound right…

[D_Frag]

Close Phlosphr, but backwards. General rule of thumb is that the colder a liquid is, the more gas it can hold in solution (if it’s in solution, it’s not visible as bubbles). So, the bubbles you see in hot water is the result of a loss of gas (air) solubility in the water as it was heated. As the water was heated, it eventually became overly saturated with air, and the air came out of solution and formed the bubbles you see. This loss of disolved air in the water is also the reason hot water tastes different than cold water.

Similarly, carbonated drinks will keep their “fizz” longer if they are kept cold.

[cdhostage]

Well it’s not always gas, although I must admit that my own recent experiment did clear up remarkably after 10 seconds sitting in a clear glass.

There’s still a lot of particulate stuff in there though…

I wonder how many more meters of pipe that water has to go through to come out my hot tap instead of my cold.

[False_God]

Yep, sometimes there will be more particulates in hot water than in cold. The reason? It sits in the hot water heater and the sides of the tank react with what is, after all, a solvent. So some of the coating of the tank and the minerals in the water that can be precipitated out by heat sometimes do, giving the bottom of the tank especially a cloudy appearance.

Also, regular hot water isn’t cloudy, exactly, it’s turbid from small air bubbles.