MadSci Network: Physics |
This is a very interesting question. The simple answer is yes, the salt water will get hotter faster. The reason behind this has to do with the specific heat capacity of water and salt water (that is, sea water). These are the only solutions that I can find reliable data for. Water has a specific heat capacity of 4.184 J/g/K. That is, for ever 4.184 joules of energy added to a gram of water, the temperature will increase by one degree Kelvin (which is the same as one degree Celsius). Heat, from a bunsen burner or from some other heating element, is measured in Watts which is Joules per second. That is, a 100 W burner provides 100 Joules every second. This means that applying a 100 W of heat to one gram of water would result in slightly less than a 24 degree rise in temperature in one second. (23.9 to be precise.) Salt water has a specific heat capacity of 3.93 J/g/K. This means that applying the same 100 W of heat to one gram of water would resut in slightly more that a 25.4 degree rise in one second. (Note that in both cases, I assuming that 100% of the heat gets into the water in the one second - that I am working at 100% thermal efficiency.) This is all a result of the disruption of the structure of the water by the salt. Water has a very high heat capacity due to the extensive hydrogen bonding network in solution. Salt (if you mean NaCl) has a lower heat capacity which means that a solution would simply be a compromise of the two heat capacities (hence, part of the reason for the lower heat capacity of the solution) but there is also a disruption of the structure of the liquid water due to the ionic components from the salt. The lower heat capacity means a faster increase in temperature for a given amount of applied heat. Hope that helps.
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