Rock salt is Sodium Chloride - NaCl. Calcium Chloride is CaCl2. When NaCl dissolves, there are two ions - one of Na and one of Cl. When CaCl2 dissolves, there are three ions, one of Ca and two of Cl. That's why Calcium Chloride works better. Both are chemical reactions - they lower the temperature at which water freezes - so they cause ice to melt as long it the temperature is above the new freezing temp.
I hate to nitpick, but isn't dissolving a physical change? You mix table salt into water, then evaporate all the water and you'll still have table salt. If it were a chemical reaction, then a new compound would have to be created.
Dissolving salts into water raises the boiling point of water and lowers the freezing point. I believe calcium chloride lowers the freezing point more than NaCl would and is why it is more effective at dealing with ice.
I always loved chemistry in college is high school.
I hate to nitpick, but isn't dissolving a physical change? You mix table salt into water, then evaporate all the water and you'll still have table salt. If it were a chemical reaction, then a new compound would have to be created.
Dissolving salts into water raises the boiling point of water and lowers the freezing point. I believe calcium chloride lowers the freezing point more than NaCl would and is why it is more effective at dealing with ice.
I always loved chemistry in college is high school.
No quite correct, JD.
Is mixing calcium chloride and water a chemical reaction?
Answer YES
CaCl2(aq) + H2O(aq) = 2HCl(aq) + CaO(s)
You con't get CaCl2 back.
More importantly for melting snow: the reaction is exothermic giving off HEAT.
(thermometer is in Celsius)
Last edited by PRBuzz; 02-07-2011 at 02:41 PM..
Given the diversity of the human species, there is no “normal” human genome sequence. We are all mutants.
Is it called the eutectic point ?
Haven't thought of it since Charlie Waughs 1972 chemistry class, all I wanted to do was burn stuff . . . . . boy did I ever.
When we use either CaCl2 or NaCL to melt ice , its because it lowers the melting point of the water. There is virtually no contribution of an exothermic reaction at the very low levels it gets diluted to when you use a sprinkle of salt on an icy surface. yes , a spoon full in a small amount of water will raise the temp but for the use in melting ice , its all Phase diagram stuff , not exeothermic reaction. It actually will lower freezing point to -50 degrees at a 30 wt% solution but my guess is that at the concentrations we use , it might lower it 4 degrees or so.
The experiment to prove this using the video shown , would to be to put the reacted mixture that was raised to 50C inot a freezer. The freezing point of the water would be way low , maybe approaching -50 C at the concentration he used. Remember , in the freezer you are not taking the salt out. You are just taking heat out and even though all the heat of the reaction is gone , the water with the same salt in it still has that hugely lowered melting point.
To read more , search for "water/Calcium Chloride Phase Diagram.
When we use either CaCl2 or NaCL to melt ice , its because it lowers the melting point of the water. There is virtually no contribution of an exothermic reaction at the very low levels it gets diluted to when you use a sprinkle of salt on an icy surface. yes , a spoon full in a small amount of water will raise the temp but for the use in melting ice , its all Phase diagram stuff , not exeothermic reaction. It actually will lower freezing point to -50 degrees at a 30 wt% solution but my guess is that at the concentrations we use , it might lower it 4 degrees or so.
The experiment to prove this using the video shown , would to be to put the reacted mixture that was raised to 50C inot a freezer. The freezing point of the water would be way low , maybe approaching -50 C at the concentration he used. Remember , in the freezer you are not taking the salt out. You are just taking heat out and even though all the heat of the reaction is gone , the water with the same salt in it still has that hugely lowered melting point.
To read more , search for "water/Calcium Chloride Phase Diagram.
I like that...on a grand scale. I'm a single molecule scale guy!
If there is no water and its below freezing...each crystal/molecule CaCl2 on a molecular scale reacts with snow/ice to generate water based upon mini-exothermic reactions, e.g. ice melts. The thing cascades and makes more water which dissolves more CaCl2. The more water the more CaCl2 dissolved the lower the freezing point which causes more ice to melt.
Given the diversity of the human species, there is no “normal” human genome sequence. We are all mutants.
I am confused, doesn't the solid calcium chloride generate heat untill it becomes liquid when exposed to water, either solid or liquid?
Stay confused, sometimes we are better off that way!
Point 1: yes when adding solid/dry CaCl2 to water it will get warmer. The more CaCl2 the warmer it gets. The mixing is "exothermic".
Point 2: CaCl2 in water will lower the freezing point of that water. Again, up until 30% (w/v) that freezing point depression will eventually reach -50C. (Question: anyone know how cold -50C is? DAMN COLD!)
When determining the freezing point (or eutectic point) of a given solution of CaCl2 in water it doesn't matter at what temperature the CaCl2/water solution starts from, it is not a measure of how many BTU's to cool only at what point does the solution freeze. So if I take room temperature water, add CaCl2 depending upon how much CaCl2 it may get detectably warm (to the hands or see movie above), then cool it down to freezing it will still have the same measured freezing point whether I start from room temperature water, warm/hot water, or even cold water. The graph attached earlier takes 20 or more different solutions of CaCl2 in water and measures the freezing point of each solution.
Side point: Car antifreeze, ethylene glycol, if you mix 2 parts anitfreeze with 1 part water you get a solution that freezes at ~70C. Don't mix ratios in any greater as the freezing point rapidly rises!
Given the diversity of the human species, there is no “normal” human genome sequence. We are all mutants.
Given the diversity of the human species, there is no “normal” human genome sequence. We are all mutants.
Hybrid Mode
