Boiling point elevation and freezing point depression | Chemistry | Khan Academy

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Raising or lowering the boiling or freezing point of a solution by adding solute.
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Chemistry on Khan Academy: Did you know that everything is made out of chemicals? Chemistry is the study of matter: its composition, properties, and reactivity. This material roughly covers a first-year high school or college course, and a good understanding of algebra is helpful.
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[@Kf7tgy]

Not sure if anyone else noticed but he wrote lower boiling point when he meant freezing point at about 4:00

[@pranjuism]

+Spencer Simko yeah ..correct..even no one corrected it

[@jacktellner646]

+RAJESH PATEL :/ On the _actual_ website, just yea... XD

[@arixii3796]

By lowering the freezing point he means that it is harder to freeze, and also harder to boil as well.. Correct me if I'm wrong :/

[@Ren10Alien]

because boiling and freezing are processes that move in opposite directions, making something harder to freeze actually makes it easier to boil

[@jacktellner646]

CholoYeol Plus, freezing involves liquids & solids while boiling involves liquids & _gases_!

[@Karlwojo1]

i like how he corrects himself on the boiling point and then writes it anyway

[@gauravagrawal8141]

so is it lowering the melting point or boiling point?

[@nuurakk]

Gaurav Agrawal He wants the water molecules to get in to a crystalline form, so he means melting point (a bit NaCl in water will make the melting point drop a few degrees).

[@ryanbarrett4441]

I love how he has america's next top model on his dashboard when he is showing the sim. LOL (6:49)

[@khanacademy]

100 NaCls would disassociate into 100 Na and 100 Cl or 200 ions. Mole is just a number like 100.

[@melodysimms4835]

6:15 is why adding salt to water to make it boil faster actually does the opposite and makes it boil slower!

[@insearchofsunsets3265]

You might look at editing this one. You say lower melting point, but wirte lower boiling point. This would be very confusing to someone that is learning this for the first time.

[@gauravagrawal8141]

so is it lowering the melting point or boiling point?

[@nachiketbelwalkar1072]

dude...its lowering melting point...melting refers to solid to liquid phase...freezing refers to liquid to solid phase.....boiling refers to liquid to gas and condensation refers to gas to liquid....sublimation refers to solid to gas phase

[@dreamzzstate5909]

@@gauravagrawal8141 Addition of the solute to a pure liquid solvent causes the need for a much lower temperature for freezing, and a much greater temperature for boiling.

[@dreamzzstate5909]

@@gauravagrawal8141 Lowers the melting point and increases the boiling point.

[@azndude3600]

@taraisthelaw He explains it later. Basically, the solute will prevent water molecules to assemble into lattice structure, thus lowering the melting/freezing point. But it will also raise the boiling point because solute particles at the surface will be blocking some of the vapor from escaping. Since boiling happens when vapor pressure equals atm pressure, you would need even more heat that once needed in order to compensate for the loss of vapor pressure due to the solute at the surface.

[@jordanphillips9133]

I love how he has Khan Academy bookmarked

[@AyeshaKhan-gp9on]

7:07 "One of the neat things in life is that the answer is actually quite simple." Khan Academy getting philosophical!!

[@bigjoe7166]

ur way better than my chem teacher. im gonna start skipping chem

[@Jazlynify]

Thank you. Your video clears some things out for me.

[@Colikieo]

When multiplying the mols by the amount of ions, in your case 2, Na+ and Cl-. It would probably help if you explained the Van't Hoff Factor and add it to the equation.T = i k m were i is the van't Hoff factor. just a suggestion,love the videos by the way, Your saving several students money

[@MrShadowstar27]

Soo Sal watchu doing on America's next top model page?

[@portsmouthschoolofeducatio2698]

+MrShadowstar27 😂

[@khadijaharoonrollno32morni59]

Kindly make a video on raoults law when both components are volatile. And how raoults law is the best criterion to judge wether a solution is ideal. Kindly make it as soon as possible

[@coolinglifee]

he's the best tutor for everything

[@digiconvalley]

jazakaAllahu khairun

[@jackiefyde]

Thank you, this makes my life easy; when teachers suck cxx.

[@sreelatharaghu1748]

very educative video

[@ongcunon1982]

Dr Khan, you are an important part of my degree !

[@SofiaGonzalez-bv1hh]

Thank you :)

[@markgeromecatchillar4274]

Thank you

[@norwayte]

Thanks. I got it. Thought about it...the Mol-Thing. The origin. The definition. The number. Why they defined it. They relation to C12. And atomic mass unit...C12 again. They other way around is helpful for me... without water...100 Na and 100 Cl turn into "only" 100 NaCls. (And not 200 NaCls). :-) Thanks. You are helpful as always.

[@ByRecentDesign]

I agree. Without those little mistakes this guys videos would be awesome. As with this one, that mistake makes it even more confusing.

[@niccidell]

do you have a video doing calculation for freeze point depression for an unknown molecular compound?

[@murph8111]

thank you SO MUCH.

[@laurenreyna5779]

americas next top model, me too

[@prabhanshukatiyar4635]

when he made the ice structure, he made it square, but its acually hexagonal

[@sarahkaveh7739]

Why does that formula make sense??:)

[@curtpiazza1688]

Thanx! 😊

[@HotPepperLala]

6:42 did anyone notice that he bookmarked "America's Next Top Model"? lol

[@benewaaevelyn8301]

I love this video I am using it to teach my best friend ayva

[@RsGhost1]

You sir are an epic teacher :) I actually dropped the subject Chemistry, trying to pick it back up again. Physics REALLY helps to understand chemistry though.

[@RsGhost1]

@Jan Leunissen Funny to read a comment of mine from so long ago (wrote it during high school)! Now expecting to obtain my PhD in condensed matter physics next year. Thanks for this!

[@ThePeterDislikeShow]

I drank a -30 degree beer one time; I added CaCl2 to the beer and then cooled it down with dry ice. It would have been great except the CaCl2 affects the taste too much, giving it a pasty consistency.

[@danielbaydeutch2422]

Literally nothing in that comment is chemically possible.

[@syamsularifin7766]

thanks

[@fauzanabrar8979]

how to decrease boiling point of water?

[@himagabandara9620]

America's next top model😂...did anyone notice?

[@crisisme7]

thanks man

[@graffitiabcd]

6:30 Boiler up!

[@Colikieo]

@MrPengwin3 i noticed that as well

[@bendsmore]

I like how one of his bookmarks,when he pulls up his internet browser, is America's next top model.

[@xchizophrenix1]

hm its all independent of surface area... result is correct but surface area actually has nothing to do with it. see wiki.

[@You2ubeGuy01]

So at 3:26 should it be lower freezing point not boiling?

[@Cameron-Bradford]

I wish you were my chemistry teacher.

[@rosnibasu8762]

Awesome vid! Thank you so much! :D (Btw, 5:35 you misspelled 'pressure'.)

[@diptayandas7477]

idiot

[@1Macraman1]

3:30, lower freezing*

[@physicsworkout]

Watching just before 2 hours of my exam 😂

[@mr.nobody6392]

So ...You Are Late ..!

[@mbah9608]

Same😹

[@SuperNerd707]

what exactly is the change in temperature referring to? It is the change in temp in respect to the pure solvent? Or is it the change in respect to initial and final conditions?

[@midgetking101]

the pure solvent. However you could use the same formula to calculate initial and final conditions. Delta T doesn't have to be of the pure solvent, it can be of a solution.

[@creosotegirl]

I wish I could talk just like Carl Sagan...the way this guy does.

[@mayankjangid1543]

Amazing explanation sir ! I now started loving chemistry just because of you. Thanks a lot lot !

[@MikeHaMoshea]

Dear Dr.Khan, Your vedios are excellent, thank you. But in this one you have a small error, you do say the right thing that once something is added into water (solute added to a solvent) it lowers the freezing point and increases the boiling point, but you wrote it lowers the boiling point instead of writing it lowers the freezing point. Maybe you can just write a note on the side bar about it instead of remaking, Thank you again.

[@famguy218]

I don't get how you know so much information and remember all of it.

[@jasondean88888]

famguy218 It comes with practice and repetition. Do something enough and it "becomes a part of you". When a person starts driving a stick shift it feels like there is a million things to get right and pay attention to. Even just a few months later it can be as natural as breathing. Or for another example, working a cash register at McDonald's. When I was 16 and looked at that register with literally over 100 different buttons, and saw experienced employees able to ring up customers "in real time" without having to hunt and peck for each item it seemed amazing. 2 weeks later I was better than them. Once a person grasps that all new information will normally look way more complex than it is, it can bring a lot of confidence. Knowing that information can be absorbed and learned just like every thing else a person has done in life can demystify a topic considered highly complex. In the past, I've kept a lot of these videos on repeat for days at a time. The first time I might absorb 5% and be baffled by the rest. The second time, because I have a small amount of understanding to build on, I might get another 10%. By the 4th or 5th or 6th time, it all starts making sense. The key is to not be afraid of "feeling dumb" and understand that that feeling is (for a lot of people) a normal part of learning. If you can ignore it and push ahead anyway, progress comes a lot more quickly because you aren't beating yourself up for not understanding. That's why a person watches these videos in the first place. It's information you don't have and don't understand. You're not going to get it right away, just like driving or learning any other new skill. But eventually, chemistry or calculus, or physics, or anything else can become part of you and something you can do as easily as breathing. It's just a matter of time and repetition. Some people take more of that than others but I'll end with one if my favorite quotes: "What one person can do, another can do."

[@smashadams9811]

Solute lowers freezing point/melting point. (That's why we have a freezing point DEPRESSION formula) Solute raises boiling point. (That's why we have a boiling point ELEVATION formula).

[@SmileToday7]

khanacademy is my life

[@fleshcookie]

Sal Likes Americas Next top Model!!!!

[@InspirationIsFree]

I think Sal actually means lower the freezing point at 3:26

[@CookWithPri]

really helpful! why i didn't i discover your videos earlier in the year? haha definetly going to watch all of your vids before my apchem exam!!

[@jonatan01i]

Isn't the higher boiling point because of water having higher attraction to the solvent ions than to itself? And so the solvent keeps the water more together.

[@idster7]

@khanacademy but prof., doesn't NaCl only disassociate when it dissolves? and when it dissolves, it's no longer a solute in a solvent, right? i also have trouble intuiting why the size of the respective atoms would not make a difference in affecting boiling/melting points.

[@jesusrivera3942]

when vapor pressure and atmospheric pressure are in equilibrium, then boiling point happens

[@pirates8228]

I'm mad at KZbin for not showing this as 1st search result

[@kalsoomali1515]

and what about the graph due to boiling point elevation...??? In my text book it's so jumbled up I don't understand

[@gabrielmoore2723]

Look at that old web browser..

[@pkshabbaboy]

sir what about the melting point and also the boiling point

[@rjdizinez]

i bet he is the best a draw something

[@ninjajesus81]

From what I understand, salt has twice as much effect as glucose, since it dissociates. So does that mean it doesn't matter how large the solute molecules are?

[@supernova5618]

Ironically nobody has ever answered your question from 11y's , let me answer it. Yes it doesn't matter how large the solute molecules are.🤣🤣

[@chetes15]

In my pre-lab assignment The formula for molality is: n Solute/MMsolute x Kg solvent. Does anybody knows where the MM solute come from? In al textbooks the formula for molality is just: moles solute/Kg solvent. :S

[@potato11teen]

america's next top model 6:30 o_o

[@jaggatham]

❤

[@BTMECSatyacharanT]

Wouldn't the freezing point be depressed,if solute particles had been smaller than water molecules?

[@fannyaliyannisa8890]

good explanation. Love it. I read so many text books but no one explain how could that happen. All they talk about is entropy.

[@daniyalso4]

Fun Fact: it's 12 years old

[@thedeco7868]

14 years

[@crisisme7]

will my teacher giv me it during the quiz or should i solve for K and how?

[@Riley-ek8xs]

america’s next top model, huh?

[@crisisme7]

so.... how do u find K?

[@codosacho5924]

how do i know that vapor pressure equals the atmospheric pressure ?

[@stepheng3014]

Vapor pressure is determined by the total pressure along with the pressure of the solution. Look up Dalton's Law of partial pressure.

[@LivinCurse]

youve been watching Americas Next top model :P

[@codosacho5924]

how does sugar dissolve in water ??

[@stepheng3014]

It's based on the polarity. Glucose is a polar molecule, and so is water. Therefore, they can combine.

[@nicolesouth1716]

These videos make me happy. Have this useless comment of gratitude.

[@EthupBolt]

At 3:32, you said Solute --> Lower boiling point. Then at 6:09 you said again, Solute -->raising boiling point, what?!?

[@norwayte]

2 moles of something dissociate in 4 moles of two somethings ?! Mole is still a confusing concept.... for me....

[@YoungKiIIaX]

So do non-ionic bonds always have a value of 1 as the i?

[@stepheng3014]

It's a simple yes.

[@ouiemfrs4373]

Can someone answer me? we in the class used osmolarity instead of molality why?

[@dreamzzstate5909]

Molality is better when dealing with temperature. Osmolarity deals with volume which changes when the temperature changes.

[@Casperx9373]

Lower boiling point or melting point !! Anyone please answer

[@jasonmiller8407]

Lower melting/freezing point, higher boiling/condensing point (about to die on ap exam?)

[@shoaibheesam1577]

Wait, so more surface area=more evaporation?

[@bilqueesfatima2392]

Evaporation is a surface phenomenon. Molecules in the bulk gain energy and escape from the surface. More surface area implies more space for molecules to escape.

[@Lexyvil]

Please video, please save me from my exam in 6 hours...

[@Lexyvil]

***** Yep!

[@link2519]

LOWER MELTING POINTTTTTTTTTTT

[@christyc463]

@MrPengwin3 hahahahahaha oh dear

[@trand95]

um sal, why are you watching americas next top model?

[@missanna208802]

Skip to 4:05

[@thecoryful]

according to the video, the addition of solute raises the boiling point of a substance. If this is the case, why is it commonplace for people to add salt to water to hasten its boiling? just curious, not a smart-ass.

[@esthernaidu4390]

+Cory Christopher I have to disagree that it's commonplace for people to add salt to water to hasten its boiling. To flavor whatever is going to be cooked in that water, yes, but not to hasten its boiling. Personally, I would always add the salt after the water has begun to boil, so that I didn't have to spend extra time waiting for the water to actually start boiling. (Source: I cook quite a fair bit)

[@SkeetleSimsy]

It would be the same concept as a pressure cooker. Raise the boiling to point to lower your cooking time.

[@beautybymaya09]

?

[@tiktokwarrior129]

Who is here in 2022 🙂

[@abdelrahmansaid6450]

Lol me here in 2020

[@zippitydooda4065]

Does anyone know the freezing point of a 0.527 aqueous solution of libr???

[@lucassssyn]

2023 gang

[@mugdhabanduke5685]

Please upload advance chemistry videos

[@jaxxie_snaxxie]

SAVE ME FROM MY EXAM!!!😞😔😒😣

[@jaxxie_snaxxie]

J co until th

[@paulceltics]

just something from yahoo

[@mt439]

no offence but nobody cares about your initial misconceptions. you risk teaching people incorrect facts which they will have to re-learn later by underscoring your own errors. by the way, not everyone thinks like you: to some people it is intuitive that presence of solute will raise boiling point and lower freezing point this is a counterproductive teaching method seen in many youtube education videos. helpful: underscoring an apparent paradox; not helpful: underscoring something incorrect which you will later amend, presumably (i did not watch the video to the end)

[@herecomesabirdd]

not your best video, I think this one deserves a remake.

[@ni483]

A decade later...stfu