Sign In | Sign Up | Help | Invite    
Advanced Search Ask A Question Community Recent Changes
My:             Contributions   
Contributors
{for ul in pageInfo.page}
${ul.nickName}
{var al = toBreakWord(ul.adUrl,18)} {if ul.adSentence !=''}${ul.adSentence}
{/if} {if ul.adUrl !=''}${al}
{/if}
 
{/for}
Earn Free Advertising   +   Earn Money By Writing What You Know at WISTEME.COM
Question Discussion History

Edit
    Question ID:   18067         Current Version: 1
Question: Why would the boiling point of a liquid (take water, for example) be elevated when a nonvolatile solute is added to it?
Category: Science > Chemistry
Keywords: salt, temperature, affect, increase, liquid, water, boiling point elevation
Type: why
Rating:(0 ratings)    Views: 95    Discussions: 0   In Watch Lists: 1  

 
    Answer:

Vapor can form anywhere in a boiling liquid. If you watch a boiling pot of water you will see bubbles form throughout the water and on the bottom and sides of the pot. Also, if you pour a layer of oil on top of the water it will still boil in the same way, in particular at the same temperature, without having any exposed surface at all. The reason dissolved solutes increase boiling point is that the solute must come out of solution in order for the water to boil. This costs entropy (the entropy of solution). Boiling is entropically driven, hence the reduction in the net entropy gain of boiling results in a higher temperature needed for the reaction to go. To put it without jargon: for a little packet of water with dissolved salt to turn to steam the salt atoms must, in the course of their random zooming about, ALL simultaneously leave the packet. This is not a likely event. It becomes more likely as the temperature (i.e. the average speed of zooming about) becomes higher, though, and at a certain temperature above the ordinary boiling point it becomes sufficiently likely to allow boiling in spite of the handicap. You can also see that the effect will naturally increase with the concentration of dissolved solutes (i.e. the number of salt atoms per packet that must simultaneously leave). Incidentally, at the low energies involved here molecules are quite hard and space-filling to each other. You can regard them as little hard balls, which are as closely packed as they can be in the liquid state. That is why, for example, it is so very hard to compress or expand a liquid --- there's no space. This is the basis for hydraulic equipment, e.g. the brakes in your car.

Source: Argonne National Laboratory

Read more questions from WISTEME through
     Add to MSN Add to My AOL
 Rate this Question
   Add to Groups   Add to Watch Lists   Share Question
                          
 
    More Readings :
[QID:10591]    How does salt change the freezing point of water?  
[QID:18681]    Why does adding salt to water lower the water freeze point more than adding sugar?  
[QID:12734]    What factors affect water availability?  
[QID:13174]    Does the temperature of drinking water contribute to the amount of lead that it contains when used for cooking and drinking?  
[QID:13356]    Can the salt used for highway deicing affect the quality of my drinking water?  
[QID:17549]    Why do some salts, such as cerium (III) sulfate become less soluble in water at high temperature?  
[QID:18236]    Are there any liquids that have a lower density as a solid than a liquid other than water?  
[QID:16461]    Why does evaporation cause a cooling effect?  
[QID:19051]    Why does alcohol evaporate faster than other liquids?  
[QID:3241]    What do I need to know about the career of water and liquid waste treatment plant and system operators?  
     Question ID:  ${question.id}         Current Version:  ${question.version}

{for qh in questionHistory} {if qh.status == 'r'} {else} {/if} {/for}
Version Contributor Date (ET) Voting
${qh.version} ${qh.nickName} ${qh.date} Rejected
${qh.version} ${qh.nickName} ${qh.date} {if qh.status != 'c'} {if qh.status == 'a'} Approved {else} {if qh.rstatus == 'c'} On-going {else} Pending {/if} {/if} {else}   {/if}
Start a New Topic
ID Topics Replies Latest Post (ET)
{if dlist!=null} {for d in dlist} {/for}
${parseInt(d_index)+1} ${d.sentence} ${d.replyNum} ${d.lastestDate}
{else}
No discussion topic.
{/if}
Label Name:
 
Group Name:
 
 
{else}
     You have no group.
{/if}
Advertisements
{if advertisements.length > 0} {else} {/if}
{for ad in advertisements}
${ad.adTitle}
${ad.adSentence}
${ad.adUrl}
{/for}

Home | About Us | Terms of Use | Privacy Policy | Browse Questions | RSS Feed

Copyright ©2010 WISTEME LLC. All Rights Reserved.