Salted ice cools more sodas than regular ice on an equal volume basis. How many more sodas can be chilled by 30% salt + 70% ice in comparison to 100% ice? JMG.
salted ice requires a lower temperature to freeze, therefore it's colder. It can therefore absorb more heat.
Redrover is right. Why would the DOT put salt on the roads? To make the roads ice over? lol. No, to lower the freezing point, thus making it a liquid and safer to drive on.
If the ice is already frozen, it must be at a lower temperature than normal ice. Thus it will cool slightly more soda. The flaws in this are, of course, that 1. The ice probably isn't going to be at its melted point, unless it's surrounded by a pool of water (i.e., you left it out on the counter) 2. Most of the "freezing potential" isn't from the temperature of the ice, but rather the heat it absorbs while melting. Since salt doesn't undergo a phase change during the process, it's pretty much "dead weight." Feel free to pick holes in that analysis if you have better numbers than I do Please Register or Log in to view the hidden image! (any numbers!) I mean, at low concentrations yeah, but 30% salt sounds like a bit much... I wouldn't know though... GodLied, it's impossible to answer the question without some numeric data on the heat capacity (?) of the ice/salt and probably by how much the freezing temperature was lowered.
A question of specific heat capacity We have to compare the specific heat capacity and the latent heat of fusion for the salt water sample, and the pure water sample. This question is similiar to the fire walking phenomenon. People can easily walk over coals that are at 800 degrees C or more and suffer no apparent damage to the skin on their feet. This is due to the high specific heat capacity of the coals. I have yet to see someone walk over a hot plate at a similiar temperature, and no wonder. Metals have a low specific heat capacity and thus heat exchange is rapid. That is why fry pans are made out of metal and not glass!!!
Yes, we need to know the specific heat capacity and latent heat of salt, ice, and saltwater with no less than 30% salt by volume. Because I never said salt water, the salt is touching the ice but is not in the ice. As the ice melts, icewater mixes with salt to make salt water. Salt, saltwater, and ice have different specific heat. Saltwater of different % salt have different specific heat. That is what makes the question difficult. As the ice melts salt water is formed. Saltwater absorbs heat faster than ice. Depending on the salt used, the specific heat of the salt varies. My question was open enough to not state the shape of the salt and the ice. Using a large salt block and ice block results in slower mixing of salt and ice water. This question essentially is, will more heat be absorbed by 30% salt and 70% ice as opposed to 100% ice? Most likely, yes. Because the salt is not stated, choice of salts will alter the answer. JMG.
First off, it's not specific heat that detemines the rate of heat exchange. It's, er, something else. Specific heat is a measure of how much energy is needed to change the temperature of a unit volume of a material by a specified amount. I think I understand the coals thing, but that's different from specific heat.... GodLied, same with your answer. I am suspicious of it because, although you make a reasonable argument that the ice/salt combination might cool faster, you don't say anything about how it might cool more soda. Unless the addition of this kind of salt to water lowers the temperature of the water, H(2)O has a relatively high specific heat, and more importantly latent heat of fusion (thanks for the terminology!), so on inspection (without any data. lack of experimentation = bad) the pure ice should still cool more soda... If you have actually done it with those proportions and it turned out as you say, I am willing to concede the argument.
With charts for the latent heat and specific heat of salt, various saltwaters, ice, and water from 0 degrees celcius to 50 degrees F, we can without much experiment consider if the heat needed to raise the temperature of 100% ice to 50 degree water is different from the heat needed to raise the temperature of 30% salt + 70% ice to 50 degrees F. Clearly 70% ice will cool as much as 70% of the 100% ice. So, the question remains, will 30% ice and 70% water absorb as much heat as 30% salt which gradually became 30% saltwater at 100% volume? Such a question needs to know the melt rate so that the heat absorbed by salt and different volumes of salt water become known. Without the melt rate it is hard to know the answer. If however we separate the salt and the ice so that melted ice will not mix with the salt, the answer is easy because we need only compare the cooling capacity of 100% salt and 100% ice where each is cooled as cold as they can get at 32 degrees F so that ice may have all of its latent heat. So, will salt on a volume basis absorb more heat than ice to go from 32 degrees F to 50 degrees F? I do not know. JMG.
You just need to know the specific heat of the mixture, its temperature, and the surrounding temperature. When the mixture goes to the temperature of the surroundings, it will absorb an amount of energy given by: Q = mC<font face="symbol">D</font>T where C is the specific heat, m is the mass of the mixture and <font face="symbol">D</font>T is the temperature difference.
There is more than one specific heat. The specific heat of saltwater depends on the salt concentration of the water as well as the temperature of the water. Any latent heat in the temperature change changes the simple equation you have given. For example if the ice is 31 degrees F and the salt is 31 degrees F, there is latent heat in the ice which must be absorbed before ice changes from 32 degrees to 33 degrees F. JMG.
Case 1: Start with X kg pure ice. Add sodas. Case 2: Start with 0.7X kg pure ice, 0.3 kg salt. Add sodas. Assume initial temperature of soda and salt is the same in each case. Assume initial temperature of ice is the same in each case. Assume enough time is allowed in each case to allow water, salt, and soda to reach equilibrium. Assume negligible heat is absorbed from surroundings. Assume target temperature of soda is the same in each case, and is > 0 degrees celsius. The problem given is to compare the number of sodas that can be added in case case before the equilibrium temperature exceeds the target temperature. Off-the-cuff answer: The pure ice will cool about haf again as many sodas as the ice-salt mix. However, if a shorter cooling time is specified, the ice-salt mix may cool more. If the ice-salt mix is determined on a volume basis rather than weight, it will depend heavily whether the ice is crushed, cubed, or block.
My prior assumption was ice, ice cold salt and sodas. If the salt is ice cold and sodas are as cold as the salt, the sodas are as cold as ice and are already at thermal equilibrium. With sodas at the same temperature in each case, no sodas may be cooled because all sodas are at thermal equilibrium with ice. My query involved ice and salt at the same initial temperature, not sodas and salt. If salt and sodas are at room temperature, less sodas will be cooled with less ice because that ice has to also cool the salt. If salt is at the same temperature as ice, salt alone will cool some sodas. That is why the answer is not simple. JMG.
Yes, salt changes state when in contact with water. The salt chosen determines the effect of the change of state. For example, NaCl reacts differently than CaCl when immersed in water. That is why salt is not dead weight and why the choice of salt alters the answer. For example, some salts bond with water which either makes or absorbs heat from the surroundings. The water bonding principle is why a particular salt is added to cement when it is desired to have the cement dry faster. Chemical reactions do alter the heat absorbed by the salt and ice mixture. Thank you for advising others of the chemical change of salt in water. JMG.
Given two zipped ziploc bags, one with ice cubes and one with salted ice cubes. Each bag has a fan blowing wind on them to help evaporate any condensation outside of the bag. Since you find the salted ice will not be colder than the ice, see which hand gets frost bite first. Once your hand holding the salted ice freezes, get an artificial limb and learn more about science the hard way. JMG. JMG.
Oh, I forgot, use enough salt to end up with 30% brine when the ice has melted. That will ensure your hand will freeze. JMG.
I'm sure that adding a lot of salt to your ice would cause all sorts of interesting things related to the rate at which the ice melts and the specific heat of your salt water etc, but I can't imagine that it would be enough of a difference to make up for a 30% reduction in the amount of ice that you have. I'm pretty sure that 100% ice would be able to cool more soda than 70/30 ice/salt.
