5.1 First Law of Thermodynamics and Enthalpy | General Chemistry

Chad introduces the topic of energy and its units, comprehensively covers the First Law of Thermodynamics, and introduces Enthalpy. First, a basic definition of energy is provided and the Joules, calories, and nutritional Calories are introduced. The First Law of Thermodynamics is then covered both qualitatively and quantitatively as described by the equation:
DE = q + w
Calculations involving the flow of energy between system and surroundings through heat and work are explored.
Enthalpy is then introduced with a basic definition along with the definitions of Endothermic and Exothermic as types of reactions. An application of enthalpy to stoichiometry (thermochemical stoichiometry) then follows, and the lesson is concluded by describing/defining the six fundamental phase changes and the enthalpy associated with each.
I've embedded this playlist as a course on my website with all the lessons organized by chapter in a collapsible menu and much of the content from the study guide included on the page. Check this lesson out at www.chadsprep....
If you want all my study guides, quizzes, final exam reviews, and practice exams, check out my General Chemistry Master Course (free trial available) at www.chadsprep....
00:00 Lesson Introduction
01:04 Energy, Joules, and Calories
02:48 First Law of Thermodynamics
11:23 Enthalpy
19:26 Enthalpy Stoichiometry
23:29 Enthalpy and Phase Changes
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[@verano.violet]

In just 10 minutes, You have explained to me what 3 different chemistry lecturers have failed to help me understand. Thank you so much.

[@ChadsPrep]

You're welcome - Glad you got the help you needed!

[@genebelcherskeyboard]

god bless you mr clean

[@ChadsPrep]

HA! I don't remember the last time I saw that character in an ad.

[@michailtimanov1841]

Sound and clean explanations! Nice, Chad!

[@ChadsPrep]

Glad you liked it!

[@BOB_VOX]

Mr. chads, i have a question about enthalpy, so what is it basically and why is it related to q at constant pressure

[@veselinavolik3002]

Hi hi!! thanks so much, these videos are so so amazing!! would u be able to make a video on steady state approximation for rate laws? that would literally be the best thing in the worldddd

[@ChadsPrep]

I don't have it on youtube, but you can watch a video here where I derive the Michaelis-Menten equation for enzyme kinetics which has the steady state approximation as its foundation. www.chadsprep.com/chads-elementary-biochemistry-videos/4-2a-derivation-of-the-michaelis-menten-equation/ Hope this helps!

[@timothywheeler671]

the state function concept could simplify the conservation of energy -> I spent so much time in Physics trying to reason conservative and nonconservative forces (energy that leaves the system)

[@ChadsPrep]

Hey Timothy! Hope the video helped :)

[@justahugenerd1278]

<a href="#" class="seekto" data-time="1479">24:39</a> got a good laugh out of me haha

[@ChadsPrep]

[@Allisons-analysis]

same. A much needed one 😂

[@francinebissereth5682]

<a href="#" class="seekto" data-time="1250">20:50</a> don't we need to find out the mole, how did you know there was only one o2

[@Uriakatos]

the stoichiometric coefficient of the reaction. Essentially, that conversion factor of -572 kJ/1 mol O2 is another way of writing -572 kJ of energy per mole of O2. In other OTHER words, it is saying "there are 572 kJ of energy produced for each mole of Oxygen that is consumed." This is simply a true statement based on the chemical reaction and is not subject to how many moles of Oxygen are actually present.

[@timothywheeler671]

s.o to AZ 🇺🇲

[@alexsheremett3097]

May I ask you a little question to tell you the truth I didn't understand the real concept at 20: 30 when we were looking for enthalpy change for 3 moles of O2 you said that you can't just multiply Δ H by 3 ... and to get the right result that's what exactly we (you) did Thank you in advance

[@dj69321]

He said you could actually, but then went on to demonstrate the math, which isn't necessary for this problem but is helpful to understand for more complex scenarios

[@alexsheremett3097]

@@dj69321 thanks🙏.... You know it's amazing I studied long time ago chemistry... In French!... For several decades now I didn't understand the core concept of acid base balance and general chemistry in general... Thanks to this guy and after 65 of his lectures I can say now that everything became more clear... At the beginning I started to review some French books but to my big surprise nothing has changed in their program... Stil everything is understandable... Thanks one more time for the feedback

[@FrontierThesisYU]

I know they're equivalent and that it just depends on convention, but why would my Physics textbook and my MCAT prep books use the equation: "deltaU = Q - W", in which case the work done ON the system is NEGATIVE? Meaning, why use a minus instead of a plus? Seems far less intuitive than the way you teach it.

[@ChadsPrep]

Just to be clear we are talking about ΔE = q + w?

[@ChadsPrep]

ΔE and ΔU are used interchangeably and both equations are correct... but we have to be clear on what W is: when you see +W we are assuming that work is being done *on* the system (and so adds to the internal energy), when you see -W we are assuming work is being done *by* the system (and so is subtracted from the internal energy). A lot of text books use ΔU = Q - W, but check what the definition of work is in that case. My advice as always is to follow the equation used by your Professor!

[@FrontierThesisYU]

Thank you! Do you have. Also, do you have videos on isothermal, isobaric, adiabatic, etc. processes, please? @@ChadsPrep

[@ChadsPrep]

@@FrontierThesisYU In my physics playlist: www.chadsprep.com/chads-general-physics-videos/first-law-of-thermodynamics/

[@FrontierThesisYU]

Thank you!!! @@ChadsPrep

[@estimatingonediscoveringthree]

Is dna subject to entropy

[@ChadsPrep]

Perhaps you mean "Is the existence of DNA a violation of the 2nd Law of Thermodynamics?" A little bit of a loaded question, but if you looked at a piece of DNA inside one of your cells let's say, then it's production would in no way be a violation of the 2nd Law of Thermodynamics. However, if you want to ask about not whether a particular existing piece of DNA exists but perhaps how the 1st piece of DNA came into existence or something along those lines, it is not so clear cut. A dogmatic naturalist might say that there is no violation where as a dogmatic theist might claim that there is a violation. I might be willing to say at the very least that the origination of something as complex as DNA is surprising in light of the 2nd Law of Thermodynamics. That's my diplomatic answer :)

[@estimatingonediscoveringthree]

@@ChadsPrep should we expect unmaintained dna to degrade to non-function, like in a virus

[@estimatingonediscoveringthree]

Thank you!

[@estimatingonediscoveringthree]

@@ChadsPrep appreciate all your hard work!!!!

[@ChadsPrep]

Perhaps, but that word 'unmaintained' is a little vague. But there are exonucleases and endonucleases that are fairly prevalent that will commonly 'degrade' DNA. But many of these don't require ATP which means they're carrying out processes that are spontaneous and are just speeding them up. So perhaps we might expect DNA to degrade to individual nucleotides or even further over time even without the aid of exo- and endonucleases.