Science help please !

[Oreo]

First off i'm a n00b at science.

But, just a few minutes ago i was far to hot in my room so went and got a glass of water, with loads of ice (about 10 cubes, basically filled a pint glass 2/3rds up with them), and then i put the glass under the tap and filled it with water as you do.

Out of boredom and me being an inquisitive kind of person, i decided to measure the temperature of the water. 5c to start, dropping quickly..4c..3c..2c..1c..0..-2...-4...-5, and there it stopped. -5c. Ergh, what, how ? it's still water.

And this has left me very confused. At first i assumed the movement caused by me drinking it was preventing it from freezing. So i let it settle for a few minutes, yet still no freezing. How can this be so ? Water is substantially below freezing and yet it is still just water.

This must happen everytime i have ice in my drink and i've never really thought about it.

Clever people answer me ? i can't sleep when i have something like this bugging me And yes i've googled it, unsurprisingly "Why doesn't my drink freeze when it's full of ice and is at -5c ?" doesn't bring up many results. I know about being able to supercool water, but from what i can tell this is only possible with pure water when you cool it very slowly, two things i havn't done.

 

[Roark]

Trick question, your thermometer is broken.

 

[S0ULphIRE]

Well for a start, 0c is the temperature at which pure water freezes. The water in your tap will have impurities, lowering freezing point.
Secondly, ice will be colder than 0c. Once you put those two things together you get water that's < 0 and still liquid.

edit: experiment here!
At sea level..water freezes at what temperature? - Yahoo! Answers

 

[Oreo]

Trick question, your thermometer is broken.

It's about a week old, and is actually spot on accurate

Well for a start, 0c is the temperature at which pure water freezes. The water in your tap will have impurities, lowering freezing point.
Secondly, ice will be colder than 0c. Once you put those two things together you get water that's < 0 and still liquid.

edit: experiment here!
At sea level..water freezes at what temperature? - Yahoo! Answers

Bah, i wouldn't of thought my water is that impure. My freezer is only -10c and that had no problems making ice cubes.

 

[patonb]

Well, its easy to have a super cooled liquid, and salt will decrease the freezing temperature of the water. BUT I hiughly doubt yhou did any of theses, as the water was not over salty, as you drank it.

As it being a super cooled fluid, i doubt that too. The impurities in the water will actually keep this from happening. Ice forms on Nucleation sites like the impurities in water.

My bets on you have the thermometer in a spot that it is sensing the ice cube, which is at -10C ish, and not the actual water.

 

[Trotter]

My bets on you have the thermometer in a spot that it is sensing the ice cube, which is at -10C ish, and not the actual water.

This. Definitely.

 

[overlord20]

Experiment:

- Get glass of ice water
- measure temperature
- leave thermometer in the water
- remove ice cubes
- record temperature

haha!

 

[Oreo]

Well, its easy to have a super cooled liquid, and salt will decrease the freezing temperature of the water. BUT I hiughly doubt yhou did any of theses, as the water was not over salty, as you drank it.

As it being a super cooled fluid, i doubt that too. The impurities in the water will actually keep this from happening. Ice forms on Nucleation sites like the impurities in water.

My bets on you have the thermometer in a spot that it is sensing the ice cube, which is at -10C ish, and not the actual water.

This. Definitely.

Nope, not quite that bad at science. Ice floats, thermometer was at the bottom. I'm going to record this on my phone and upload to youtube, then you no believers will see

 

[Apokalipse]

Most of these have been said, but I'm going to go with:
* Pressure - atmospheric pressure is not constant
* Purity - the presence of other molecules can affect freezing point, for example antifreeze
* Your thermometer is not 100% accurate

When water forms ice, hydrogen atoms from one molecule will bond with the oxygen of another molecule

This structure is also why ice occupies a larger volume than liquid water.
Impurities can prevent these bonds from occuring.

 

[Oreo]

Most of these have been said, but I'm going to go with:
* Pressure - atmospheric pressure is not constant
* Purity - the presence of other molecules can affect freezing point, for example antifreeze
* Your thermometer is not 100% accurate

When water forms ice, hydrogen atoms from one molecule will bond with the oxygen of another molecule

This structure is also why ice occupies a larger volume than liquid water.
Impurities can prevent these bonds from occuring.

I may have made a tiny mistake. I have a feeling i incorrectly measured the temperature

I said i was going to make a video of it again, and i did, but after 20 minutes of putting lots of ice into a cup of water, the lowest i got it was about 0.2c, this in itself was odd. I kept putting ice into the cup out of the freezer which is at -10c. But somehow this -10c ice refused to budge it from 0.2c point it reached after the first 10minutes.

That said, i don't see how i could of read it wrong. It's very clearly marked, and i use it quite often. I would of had to have a total fail to not realise it wasn't in the red (below freezing) zone.