How does ice cool water it sits in?

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

@kritiper
The water gets colder without the dilution.

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.

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

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

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

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.

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

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.

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.

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….

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?

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

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!

@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.

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.

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

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

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

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.

I think there is some magic going on there.

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.