General Question

Ltryptophan's avatar

How does ice cool water it sits in?

Asked by Ltryptophan (10269points) August 8th, 2018

It seems to me this is not an obvious event. There must be some advanced thermodynamics going on?

Observing members: 0 Composing members: 0

29 Answers

kritiper's avatar

When ice melts, it absorbs heat. The water it sits in becomes diluted with the cold water.

ragingloli's avatar

@kritiper
The water gets colder without the dilution.

LostInParadise's avatar

By the first law of thermodynamics, heat flows from a hotter source to a colder one. Heat flows out of the water into the ice. The loss of heat causes the water to get cooler.

stanleybmanly's avatar

we’re all stating the same thing. Another way of putting it is that the fluid “seeks” a uniform temperature throughout the container.

ScienceChick's avatar

Entropy. It’s the second law of thermodynamics. https://www.youtube.com/watch?v=pQ-yrGp8sfQ

stanleybmanly's avatar

@ScienceChick It’s a law full of profound implications.

ScienceChick's avatar

Here is a cool example of the first law,, but it isn’t the melting of the ice in the drink, it is if you put a bottle of beer in a bucket of ice and cool it off and you can increase the rate by adding salt to the bucket of ice.

ScienceChick's avatar

@stanleybmanly What? Are you saying you have a hard time understanding the second law of thermodynamics? It’s somehow ‘profound’?

Response moderated (Writing Standards)
Response moderated (Writing Standards)
Response moderated (Writing Standards)
Response moderated (Writing Standards)
Response moderated
ScienceChick's avatar

Actually, the 2nd law of thermodynamics has often been forgotten when it comes to things like the age of the Universe and String Theory and looking at things as systems in quantum mechanics. Uhrg…. I have office hours on Friday and it’s another year starting…. blah blah blah… as they say.

kritiper's avatar

You can have ice that is 32 degrees and you can have water that is 32 degrees. The difference is BTU’s. Things like this happen when a change of state takes place.

ScienceChick's avatar

If you really want to learn about this, Khan Academy is really good. https://www.khanacademy.org/science/chemistry/thermodynamics-chemistry But I don’t know if it’s your thing or not….

Ltryptophan's avatar

Thanks a lot everybody. =D

Let me see if I have this right: The ice is melting because it’s in contact with the air, water, infrared light, xrays, radio waves, etc. etc. The air and water are warmer for all the reasons that they had to be water just before they were poured in the glass. Now the water or air or both are touching the ice and the heat that is in the air or water is desperate to channel itself into coldest place until there is equilibrium.

So, as the heat transfers into the ice cube, a state change begins to occur on the ice’s surface. The ice is turning into liquid water just at or above 32F. This newly liquidated water then starts to move its molecules into the areas of the water where the temperature is higher. In the process of that all the water starts losing heat, and the temperature lowers. Eventually there is enough absence of heat in the glass that the water molecules in the air start to condensate on the glass further heating up the glass and its contents.

Right?

Response moderated (Writing Standards)
stanleybmanly's avatar

@ScienceChick What I meant was that some profound things arise from the simple statement that molecules will distribute themselves uniformly in a container.

Response moderated (Writing Standards)
kritiper's avatar

What is a BTU?
A BTU is the amount of heat it takes to raise one pound of water one degree C. at sea level. So, by the same token, when one pound of water is cooled one degree C. at sea level, it looses one BTU.
BUT!-
It takes considerably more BTUs to melt one pound of ice that is 0 degrees C. into one pound of water that is 0 degrees C. (I can’t remember the exact numbers, but it seems as though it is 28 BTUs.
In comparison, again, if my memory isn’t too far off, it takes 128 BTUs to turn one pound of water that is 100 degrees C. into one pound of steam that is 100 degrees C.
So you see, a change of state meaans a lot!

zenvelo's avatar

@kritiper A BTU raises the temperature of a pound of water one degree Fahrenheit.

It takes 144 BTUs to melt a pound of ice. So putting a lb of ice and a pound of 72 degree water into a calorimter, the water will cool to 32 degrees while only 5/18ths of the ice will melt.

kritiper's avatar

C. or F. the point remains: it takes a lot of BTUs to melt ice and that answers the OP’s question.
Like I said, “if my memory isn’t too far off,” which it was, and I didn’t have my college notes handy.
It’s the change of state that makes the difference. It’s how the A/C in your car works.

stanleybmanly's avatar

How did British Thermal Units wind up being measured in pounds as opposed to kilos?

Dutchess_III's avatar

Soooo…which would stay frozen longer, one large block of ice with 6 sides, or 300 cubes of ice with six sides each?

zenvelo's avatar

@stanleybmanly Because it is based on British Imperial units, not that silly French metric system with no relation to the physical world.

stanleybmanly's avatar

The big block would last much longer. The ratio of surface area to mass is so large for the tiny cubes, that a huge percentage of the total mass is exposed to the heat.

MollyMcGuire's avatar

I think there is some magic going on there.

ScienceChick's avatar

It only appears magic for those not privy to the knowledge. A C Clark said, “Any sufficiently advanced technology is indistinguishable from magic.” We know enough about physics, since the mid 1850’s to know… Not magic. Science.

Answer this question

Login

or

Join

to answer.

This question is in the General Section. Responses must be helpful and on-topic.

Your answer will be saved while you login or join.

Have a question? Ask Fluther!

What do you know more about?
or
Knowledge Networking @ Fluther