starwiz

Exactly.

If that's true, then how can we measure a specific heat for ice? Look here if you don't believe me: http://dbhs.wvusd.k12.ca.us/Thermochem/Time-Temperature-Graph.html They talk about starting ice off at -10 degrees. I promise, it's possible.

Ice definately isn't always at 32 degrees. If it's -50 outside, it might take a while for the snow to get that cold, but I'm certain that it will, given enough time. When ice gets colder, it releases heat. But as far as I understand, that heat goes to whatever's cooling it, by the definition of something's cooling something else.

I'm pretty sure you're right. However, I was unable to find anything authoritative to back me up. Do you have something that I can wave in my teacher's face?

That's exactly what I told my chemistry teacher, and she doesn't agree with me. Hm...

That's what I thought. What you're saying is true, but it doesn't apply in this circumstance. Water has a very high specific heat. That means that it takes a long time for air outside to cool it to a freezing point. So once the water cools, the grape will cool more quickly than if it were in air of the same temperature, but until the water cools, the grape will stay warmer. Since the frost is (in theory) over in the morning, the ice isn't there forever, and so the idea is that the time it takes for the ice to freeze more than makes up for the increased cold-transfer between the ice and grape. Still, my question stands...any other ideas?

We were having a discussion in chemistry class today, and I wanted to see what you guys thought about it: Temperatures lower than twenty-eight degrees F damage grape vines. Grape growers often spray water on their plants before a night when the temperature is expected to drop below freezing to keep the grape plants from being damaged, and the technique works. Why? We've agreed that the water on the outside of the grape will freeze before the grapes themselves will. I hold that because of this, the grape will maintain a temperature higher than freezing for a longer period of time: the cold takes longer to get to it since it has to freeze the water outside the grape first. I'm told that I'm not totally correct. In order for ice to melt, it must absorb a heat of fusion. Thus, when ice forms, heat must be released. While some of this heat travels to the cold air outside, some of that heat, I'm told, travels inside to warm the grape. I have a lot of difficulty buying that. As I understand, when the water freezes, heat has to be removed from it; the difference between removing and giving off heat is important. When something radiates heat, that heat travels in all directions, so in this case, if the water radiated heat when it froze, it'd certainly warm the grape. However, since the heat is just removed, the heat is transferred only to the cold air outside. So what's correct? Can anyone give me something authoritative that explains this so I can finally put this argument to rest? Thanks a lot... -Starwiz