What’s the Point of Molality?!?

Published on September 7, 2012 by

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Molality is not as common as molarity, and it has a funny name. What is the point? Molal solutions can be easier to make than molar solutions. Also, molality doesn't change as solutions expand and contract, so they stay constant while molar solutions can change. So even though molarity is more common, there are some advantages to molal solutions.

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  • ItsaStringThing 10 years ago

    Love it man. You are seriously the next Bill Nye the Science Guy. Your videos are like that Khan guy, only better. You’re more interesting, there’s no weird black background and you’ve got sweet prepared flash cards. It’s always a pleasure to see you bust out a new flashcard! Seriously, I really appreciate how well thought out your videos are, easy to follow, and visually clear and compelling. A+

  • Ghost572 10 years ago

    These videos are great at explaining sciencetific concepts glad you keep posting them!

  • Uchiha Madara 10 years ago

    Man you are good .. thanks for clearing that up .. keep up the good videos!

  • Marmora Monty 10 years ago

    thank you so much for this video rellay now I know more thing a bout moliraty and moliality

  • Vicky Jones 10 years ago

    thank you so much i now actually understand why we have to use molality!!! 🙂

  • j lindholm 10 years ago

    i love guys in pink:)

  • jhmasoud 10 years ago

    That was beautifully done. Thank you.

  • Chelsey Williams 10 years ago

    Excellent video! I’m a visual learner and this was great.

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    such a fabulous teacher. This is my first time viewing your videos and I will definitely be returning.

  • Ammar Tighezza 10 years ago

    Tres intéressant!

  • chris-anne corporan 10 years ago

    Tyler I feel like I owe you a hug. Thanks so much.

  • Tejas Praveen 9 years ago

    Brilliant! Your lessons are amazing!

  • taittinger78 9 years ago

    your videos have saved me many many times…you are an amazing educator….now to find a Tyler Dewitt of physics. 🙂

  • Vedrfolnir 9 years ago

    Great videos! Thanks! As you point out, Molarity is tempurature (and pressure?) dependant where as Molality is not. Frequently, it IS easier to weight out the mass of solvent and get Molality — but the referenceing calculations or literature might reference Molarity. If I know the tempurature AND eqn of state for my solvent, I can grind through the algebra and convert to Molarity. Could you demonstrate any simple techniques for converting back and forth between Molality/Molarity?

  • Malu Moura 9 years ago


  • xxtravisxxify 9 years ago

    Even a baby can learn chemie with you.Thanks!

    • Chhavi Gupta 6 years ago

      xxtravisxxify no a baby can’t… wht if he/she doesn’t even understand English

    • Cary 6 years ago

      xxtravisxxify eh I wish I could have been this baby lol

    • Metro Mine Chemicals 2 years ago

      @Chhavi Gupta hahaha😂😂😂

  • i Fisher 9 years ago

    do you have problems in molality?

  • the greenery 9 years ago

    so then why use molarity

  • Craig Kasper 9 years ago

    Great job!

  • Waleeja Rashid 8 years ago

    But doesn’t water expand when it freezes?

    • Tyler DeWitt 8 years ago

      Good question. Yes you’re absolutely right that water expands when it’s frozen solid (to make ice), but before this phase change happens and the water is still liquid, cold water contracts and hot liquid water expands.

      • Far Deen 3 years ago

        Then you are saying it happens instantantly , ain’t it a gradual change @Tyler DeWitt

    • Waleeja Rashid 8 years ago

      Ah okay, thanks!

    • Kevin Martin 7 years ago

      +Tyler DeWitt I did not know that! That’s so cool hahah get it cool

    • Manoj Kumar 2 years ago

      @Tyler DeWitt yeah

  • travolta levis 8 years ago

    Thanks a lot

  • Caroline Mifsud 8 years ago

    Thank you so much!

  • DaOttomans92 8 years ago

    Can you do Molality problems?

  • gamingLegacies 8 years ago

    another advantage of molality is that it’s used for in finding the change of boiling point and freezing point.

  • S M 8 years ago

    Great explanation!

  • Keiran Field 7 years ago

    Your videos have helped me so much, thanks !

  • Allyssa Reyes 7 years ago

    hi, your videos helped me a lot with my assignments and reviewers.. can you replace our teacher? LOL
    can you make a video about Dilution problems? and parts per million (ppm)?…

  • Rex Rivera 7 years ago

    thank you sir, you’re a good teacher, i salute you!

  • Rex Rivera 7 years ago

    sir. how about when it has density given in the problem?

    • Cristiano Aryam 5 years ago

      Rex Rivera density= mass/volume. if you have density and mass OR volume, you can find the third quantity

  • Arif Majid 7 years ago


  • Nat S 7 years ago

    you are awesome!

  • M.a Kanku 7 years ago

    hey Tyler just wanted to say thumbs up man, started with my engineering degree which has a lots of science and maths and your videos are helping with get through the heavy load of work ……….. YOU ARE AMAZING !!!!

  • Vishant Lama 6 years ago

    But if you increase or decrease the temperature, doesn’t water evaporate making the kg of solvent decrease or increase ultimately changing the molality of the solution.

    • Tyler DeWitt 6 years ago

      That’s why bottles have tops. If you are careless and allow water to evaporate from a solution, there is no effective way to measure or explain the concentration.

    • Palani G 6 years ago

      +Tyler DeWitt Hey come on have u stopped posting videos.That doesn’t sound good.I am simply blank on equivalent weight and methods of determining the eq.mass,eq.mass of acid,base,salt.Plz its too urgent.I am having exams this saturday,Plz post the vidoes on this topic within 2,3 days.Plz,this is my humble request.

    • Rohan Gunjal 6 years ago

      C’mon you could have used a cork on the flask.

  • Ahmed Halim 6 years ago

    Mr. Tyler, I know that the liquid water has a higher density than ice. Doesn’t that mean the less temperature , the less density, the more volume ?
    or the case of the less density is just it change from liquid state to solid state ?

    • Miguel Bruzual 6 years ago

      The density of water reaches its higher point nearly 4.0 °C, so from that point, wherever you go, it becomes less denser. Imagine the top of mountain, even if yo go one way or another you always descend, so, the higher is the temperature (from the 4.0 ° C mark) the lower is the density (higher volumes)

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    i love ur vidios ur teaching style is awsome.. U r the best teacher in the world …

  • Vinay Arya 6 years ago


  • Judith Mbita 6 years ago

    you should also try teaching maths

  • Himanshu Das 5 years ago

    yes….. best teacher in the world,

  • Roberto Laiz 5 years ago

    This is such a huge help thank you!

  • Rohit Nair 5 years ago

    excellent explanation sir…you have turned out to be my home tutor …thanks a lot !!!

  • Curiosity Squared 5 years ago

    No textbook can even come close to what you’re explaining ability is. Thank you.

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    Best. Teacher. Ever.

  • Saliha Benkhaled 5 years ago


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    Sir is there any video about common ion effect??

  • Erica Lesko 5 years ago

    Super Helpful

  • Sulu Sulfath 5 years ago

    nice explanation and attractive

  • Maria Garcia 5 years ago

    Can you please do a video that will show us how we do Molality problems?

  • Vinita Dixit 5 years ago

    sir I have one question, in qualitative analysis can be use Na2 s at the place of Hydrogen sulphide,

  • Alice Chalwe 4 years ago

    You re the best… thanks

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    Sir your videos are extremely helpful to me.you created me interest in chemistry.please upload videos in organic chemistry also

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    I have one doubt mr. Actually how to prepare 3gram of samples like a organic or inorganic products

  • Jegannathan.A Anantharaman 4 years ago

    Excellent Job. Best wishes. Thank you so much

  • Shawal Khan 4 years ago

    Plz tell about the temprature dependency of molality and molarity

  • Dhananjay Navsar 4 years ago

    v nice

  • Eslam Soliman 4 years ago

    Best teacher in the entire universe. Regards from Egypt the cradle of Science

  • Avan Atroshy 4 years ago

    Thank you sir this helps me alot😉💙

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    You’re way better than my professor at the university. She’s way too cranky when she teaches Chemistry

  • Aniket Bera 4 years ago


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    i think this exam i might pass

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    Man I learnt more in your videos than in my whole year at school.

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    you are explaining it much easier than any of my teachers, thank god that you exist:)

  • MED التقني 3 years ago

    thank you so much

  • Minami Sensei 2 years ago

    should’ve just not let molarity exist man ._.

  • Jully Ray 2 years ago

    Your awesome. Do you know how my teacher taught. She just gave me the formulas saying as definition and didn’t explained. She always forces me to come to Your channel.

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  • The education elixir 2 years ago

    I even made a YouTube channel that’s inspired by you sir! Thank you for being my inspiration. Hats off to you Sir

  • Gina Nobile 2 years ago

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  • Roger Scott Cathey 2 years ago


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