Quantum Physics of Endothermic and Exothermic Reactions Simplified!

[@ArvinAsh]

Thanks to Storyblocks for sponsoring this video! Download unlimited stock media at one set price with Storyblocks: storyblocks.com/ArvinAsh

[@jewiesnew3786]

9:59 : your periodic table is outdated Mr. Arvin!

[@AntonJoseJoseph]

Thanks .

[@dimitriosfromgreece4227]

AMAZING VIDEO BROTHER ❤️💚❤️💚❤️💚❤️🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻

[@kirkthiets2771]

You need to make at least one video per day until the election is over. At least your videos leave me dumbfounded in not a bad way.

[@peterburgess9735]

You didn't quite get to the why of energy levels being lower for bonded molecules than free atoms. You mentioned the Pauli exclusion principle and schrodinger equations, but didn't in either case state the reason they demand lower energy states for bonded atoms's electrons

[@sphinxtheeminx]

As an older viewer without much physics learning, in all the years I've been watching your presentations, I've learned a good deal about our wonderful universe. I can't say I understand more than about 10% of it, and my memory is already so full it finds it hard to take in new stuff, but for the duration of your videos I am totally in a zone of wonder. Thank you.

[@Paulkjoss]

Same 👍🏼 Every time I watch this stuff it leaves me with a feeling of awe. There is so much we know, but much more we don’t!

[@Italianjedi7]

Your memory can never be full

[@mercerconsulting9728]

This pretty much describes how I feel as well.

[@Worker225]

Your memory is far from full my guy!

[@Practicalinvestments]

Try eating more food as both learning, and remembering use energy (try eating food rich in minerals essential oils etc preferably) when you are learning (i.e. watching these videos),, take notes in the videos and look up stuff you don’t understand until you have a surface level understanding then delve deeper into the complex pieces I personally think the brain has unlimited memory (philosophically speaking) and the reason for that is potentially quantum microtubules (actin fillaments)

[@frofa2954]

At 0:40 bottom left, melting ice is NOT a chemical reaction but a physical phase change. And certainly is not 2 H2O +dH -> 2 H2 +O2 as shown. This should really be corrected .

[@Roacoelho]

Looking for this comment... Same mistake earlier in the video. Ice melting in soda is a physical reaction.

[@joshuamorris9597]

Yep that's when the video lost me. :)

[@fig7047]

I have just started watching and I have stopped at this, too. I'm willing to let it go though, because I imagine Arvin has some help making these videos and not everyone involved in the project are chemists. It is a bit strange that someone would invent those equations, though. Thankfully, it's not a deal breaker because there's nothing fundamentally wrong with what he is saying. At the level of physics it's all just "structural changes" anyway. Some arrangements of atoms have more energy than others.

[@RichardLucernas]

It's just "reactions." Whether it's chemical or physical, they're just names attached by bearded principalities. In the very fundamentals of things, everything is physical, in fact, quantum--and not being totally understood with...

[@peetiegonzalez1845]

Hah, yeah. evaporation is not electrolysis. Seems an odd mistake to make, clearly he's borrowed some clipart from a kids science book which happened to be wrong but I'm sure he'll put a correction once he reads these comments.

[@Tann114]

Great video, I particularly liked the visual of overlaying of helium/neon onto water.

[@thingsiplay]

10/10 narration 10/10 visualization 10*10/10 sound effects

[@DanteGabriel-lx9bq]

Man chemistry truly is marvelous.

[@sagittariusa2008]

Yes, but I prefer woman chemistry 😊

[@Stanger_95]

Well I respect your opinion, but it is still a derivative of Physics. Since, I like studying things to the most fundamental level, I like Physics more well, because it is about fundamental stuff.

[@sagittariusa2008]

@@Stanger_95 I couldn't agree more. I also couldn't help myself.

[@DanteGabriel-lx9bq]

​@sagittariusa2008, hahaha, I think we agree on that.😏😉

[@DanteGabriel-lx9bq]

​@Stanger_95 And I respect yours, I know a bit of physics, more theoretical than mathematical though, the concept of entropy is beautiful and it's a physical concept that with radiation and magic numbers in chemistry is something I enjoy studying. I'm interested in what we can do with matter, so chemistry is better fit for me.

[@uriituw]

These videos are first-rate.

[@nickharrison3748]

yes. I appreciate the Multimedia you use to describe the Scientific phenomenon in your Videos. back in our school, college days, we had to rely on green/black board description given by our professors and the text-books. and mostly imagination of teachers and students. so, now its simpler to understand the phenomenon with multimedia animations.

[@StreetComp]

Not surprised we got this video after the comments from another chemistry video, this one goes much deeper and gives a more complete answer so thank you.

[@ElricX]

I was just thinking it was about time Arvin released a new video. Thanks for the upload my friend! It's always appreciated!

[@anjansharma8631]

Love these videos ❤❤ They always answer the deepest questions at the fundamental level

[@EgonSorensen]

Always eager to learn how physics works at 'its core' - Arvin Ash rarely disappoints in this... Thanks, long time subscriber enjoying your excellent content.. Thanks!

[@brendawilliams8062]

I like the continuum. Not too many vids around

[@domenicobarillari2046]

Physicist here and constant reviewer! (for my kids). Always heartily recommend your productions - thanks so much Arvin! You are ALMOST as great as my grade 11,12, and 13 teachers back at Central Tech (in Toronto, but wish we had you too back in the stone age!) Just adding that I am so glad you got to clue the lay viewer in on the idea that entropy is just as important as quantum molecular energetics in these matters. Were you afraid to drop in the term "free energy" [in any of its forms] for fear of tiring the viewer? with best regards , DKB

[@ArvinAsh]

Great to hear! I'm delighted to hear that you and your kids enjoy my videos. Indeed, my original script contained terms like "Gibbs free energy" and "enthalpy" - I decided not to introduce the terms, and the equation, because I felt I would then need to explain where the equation comes from, and how it is derived. I wanted to keep this video shorter and less complex so that people who haven't had a thermo class would get it. I may do a more complex treatment of the subject if there is enough interest.

[@domenicobarillari2046]

@@ArvinAsh Well more power to you my friend. Sounds like you have great production judgement as well as everything else. DKB

[@mercerconsulting9728]

I'm also an older veiwer. My father was a science teacher, but I never quite understood the nature of matter and energy. You're doing an excellent job explaining these things.

[@jamysalmeida18]

This is the kind of video that i like, the ones that you have to pay attention. And sometimes watch again.

[@ShlokParab]

-14:23 "..... It's all about the flow of energy; it's all about the Physics." Physicist justifying why they are eligible to win Nobeld in chemistry despite being physicists

[@ArvinAsh]

Well, all sciences are rooted in physics.

[@alistairking2743]

A more detailed look at Boltzmann and entropy, in relation to chemical/physical changes, would be fantastic.

[@jonashartmann6687]

Well if youre going to talk about the quantum mechanics of chemistry you cant really leave out molecular orbital theory. Its the easiest theory that can explain moleculr photoemission spectra and can explain more fancy molecules like SF6 BCl3 etc

[@matssimmermacher3381]

Molecular orbital theory is essentially a framework for solving the time-independent Schrödinger equation for molecules. It is, of course, true that molecular orbital theory is at the heart of modern quantum chemistry, but I believe it suffices here to say that molecules obey the Schrödinger equation, just as Arvin did. A side note: molecular orbital theory is not the only framework for describing chemical bonding within quantum mechanics. Valence bond theory permits the same and was an even earlier approach. Molecular orbital theory just became more popular because it directly relates to how modern computer programs solve the Schrödinger equation, i.e. via Hartree-Fock (or Kohn-Sham) theory.

[@exo-580]

i like the background presentations and animations,it is easy to follow whats happening.lov it Arvin 🤝

[@alistairking2743]

Exellent....coming from a chemist!

[@terraminator5441]

Thank you so much for answering the questions my teacher couldn't answer!

[@andreyassa7638]

Thanks for another great video!

[@BonesFrielinghaus]

Wow! What an amazing video and explanation...sooooo much better than my university chemistry classes. Just WOW! You anticipated all the questions I had as the video progressed...

[@epiceducation867]

I love this channel so much, I hope it keeps on growing🌟

[@LiborTinka]

What was completely mind blowing for me when learning physics is the fact that electrically neutral atoms of most elements can actually capture an *extra* electron exothermically! I thought this is only a special property of halogens with chlorine leading the group (yes chlorine is even more electron-hungry than fluorine). However, this is true for most elements - gold has very high electron affinity of 223 kJ/mol - this is the reason why gold doesn't corrode even at high temperatures, but this also means gold can accapt an extra electron forming a negative gold ion known as "auride" - it even forms an exotic compound called cesium auride (CsAu). Even alkali metals can accept electrons and form "inverted salts" known as alkalides - these were discovered in 1970 and of course are very unstable. And this is also true for hydrogen - such electron-ionized hydrogen is called "hydride" (H-). Its electrode potential is deeply negative (-2.23V) making it even more reactive than aluminium metal, displacing hydrogen even from water and reacting with violent exothermy with acids (evolving lots of hydrogen gas). Apart from noble gases, only handful of elements have *negative* electron affinity - such exceptions are magnesium, zinc and mercury, for example. This is why these metals as well as some mercury amalgams make such a good reducing agents - they give off electrons but don't really want them back. Even when in metallic (elemental) form, capturing an extra electron is thermodynamically unfavorable for them. For example, magnesium ion is especially "hard" because it mimicks the electron configuration of neon, the most noble of the noble gases in terms of electron affinity. Neon is the hardest one to ionize, even more so than helium. This property of hardness gives magnesium some interesting properties important for life (e.g. it stabilises molecules like ATP and DNA). Moreover, magnesium makes some reactions kinetically favorable despite being thermodynamically unfavourable, allowing some life-enabling complex chemistry to happen, including the magic of photosynthesis.

[@Nethershaw]

I know _some_ quantum mechanics. The way we describe the spin of a particle, like an electron, depends on some choice of axis in the description. We say "up" and "down" when we are talking about electrons in atomic orbitals, but it occurs to me that no one ever says what "up" and "down" are in reference to. Presumably, since we are talking about atomic orbitals, "up" and "down" are with reference to the direction of the atomic nucleus. I'm trying to imagine other orientations, though; parallel and anti-parallel directions relative to the dipole of the atomic nucleus also seem plausible, and probably more likely, since it isn't the position of the nucleus but its interaction with the electromagnetic field that matters to the electrons. So which is it? Is "spin up" the one where the electron spin orientation is parallel to that of the nuclear dipole? Or something else?

[@marianagyorgyfalvi3659]

At the moment when one electron approaches another, they start to hide behind the protons and then the protons collide with each other😂!

[@domenicobarillari2046]

Great question: what the books say only in an indirect way is that the particular UP of relevance at any time [for a free particle!] is the measurement axis of your device, e.g., a Stern-Gerlach apparatus. If you reflect on it, there IS no other axis that exists in an interaction-free universe. In fact once you measure it, and the S-G apparatus gives UP, say, then you must, in the absence of further interaction, get that for all future measurements in your world. This is the hardest part to "get over" for some, and you are in good company -especially some undergrads who have studied Newtonian mechanics very hard to get to university. So, what is going on, e.g., with the two electrons swimming in the 1S shell of helium? The Copenhagen interpretation says you have no right to ask, BUT that nevertheless the helium system acts as if the spin part of the electron wavefunctions are opposite (Fermi principle). IF you measure one or both, you will always get either UP or DOWN, even if the spectrometer is set to 26.456deg azimuth from geographic North, say (nothing really to do with the earth) - as long as the results for two e- indicates they are opposite. Recall that the indistinguishability axiom also states that you cannot tell which is which unless you keep them separate afterwards. To more fully answer your question as posed: if your experiment depends on the relative orientation of the electron(s) spin versus the nuclear spin, you will get a result that depends on the details of the interaction between the two ( nuclear spin coupling). For one relevant electron ,e.g., you are allowed to get aligned or anti-aligned. A classical result that depends on angle is now dependent on the relative probability of getting one answer versus the other. Hope this helped - as I humbly said, this is where you graduate to the next conceptual level .....

[@BoazBesigyeBaryabaki]

Magnificent explanation

[@LowellBoggs]

Great video! Thank you. The last part about thermodynamics was particularly surprising.

[@alhypo]

Something like a heat pump on your fridge or air-conditioner is more intuitive because you can visualize the thermal energy being absorbed inside the system and then radiated away on the outside. Or actually, you can just feel it directly by touching the radiator and feeling the heat coming off it. But an endothermic reaction feels pretty weird because the thermal energy didn't move from inside to outside. All that energy is still inside the cold ice pack. It didn't transfer to another location. It has just been locked away in some mysterious molecular vault and is no longer accessible to us.

[@lightlegion_]

Your content is truly captivating!

[@ArvinAsh]

I'm glad you're enjoying it!

[@z0nx]

Always surprisingly interesting. Is there any other channel like this? We need more)

[@atmikes1]

Once again some very interesting content. Thanks Arvin 😊

[@karlfreiha4745]

been waiting for this one

[@stefaniasmanio5857]

One word. Superb! Thank you so much!

[@g_r_x_v]

Great explanation! I recalled my chemistry teacher when he talked about spins and orbitals, he gave up before even trying to explain and just told us to memorize it 😂

[@paulmicks7097]

You're a champ Arvin !

[@emergentform1188]

Super cool, hooray Arvin!

[@XEinstein]

Entropy is usually described as an emergent property of large systems of molecules. Something that happens at macro scale but like temperature entropy usually isn't described as a property of atoms, so i wonder if in a collection of atoms in a molecule entropy can be quantfied already?

[@Dr.Strange-j7m]

Ice melting is actually a *physical change, not a chemical reaction*. Here's why: 1.⁠ ⁠No chemical bonds are broken or formed: When ice melts, the water molecules (H2O) don't change their chemical structure. They simply gain energy and transition from a solid to a liquid state. 2.⁠ ⁠Reversible process: Melting ice can refreeze, returning to its original state without any change in chemical composition. 3.⁠ ⁠No change in chemical properties: The chemical properties of water remain the same whether it's in solid (ice), liquid (water), or gas (water vapor) form. Physical changes involve changes in state (solid, liquid, gas) without altering chemical composition. Chemical reactions, on the other hand, involve: 1.⁠ ⁠Breaking or forming chemical bonds. 2.⁠ ⁠Changes in chemical composition. 3.⁠ ⁠Irreversible processes.

[@whiteShadow-yt9]

Great explanation 👌

[@axle.student]

Thanks, that was a nice little refresher in my mind :)

[@danigarcia3341]

You are a genius. Thanks for your videos.

[@Thomas-gk42]

Very nice explained and illustrated👌

[@Petrov3434]

Dear Arvin, May I offer you a suggestion for a topic -- Shell model for nucleons (protons and neutrons) in atom nucleus? I was astonished to learn that NMR (or MRI to avoid use of nuclear) is based on excitacion of (mostly odd number of nucleons so that spins are not largely cancelled) where each nucleon has a distinct energy level (conceptually similar to electrons) before excitation. According to a model, nucleon shells can also have subshells -- based on quantum numbers like angular momentum (l), radial quantum number (n), and spin (s). Many thanks in advance, Boris

[@noelstarchild]

Valance electrons are of particular interest to me ATM, however, white dwarf stars and neutron stars tip the balance and exotic matter is fascinating. Thanks as always Arvin Ash.

[@zack_120]

Enlightening episode. Succinct yet informative 👍

[@gustavoaroeira7329]

Nice video. But this is certainly college chemistry, high school even. High level chemistry classes you'll be studying stuff like XeF4, where that nice picture of atoms trying to fill their shells breaks down.

[@my-tschischlak]

Yes, very cool. Seeing things like this way, you begin to understand. To what could a "chem-Ki" lead, when you just calculate all possible ways from lets say 10 elements to absorb or release energy, without any physical tests beeing made. I wonder if we find some day very new materials never had before with details no one know before. The future is ours .) We are about to find EVERY great stuff in medicine and material-science .)

[@fig7047]

I'm a reductionist as well, so when you say at the end that it's all about the flow of energy I'm in total agreement. I do think the physics (and chemistry) of dissolving goes way beyond what we normally teach people, though. The really tricky stuff we never talk about. For example, we tell people that ionic bonds are strong. So, to melt sodium chloride it takes a lot of energy (the melting point is 800 degrees C) and that makes sense. Yet, salt dissolves in water at room temperature without any trouble at all. This "reaction" isn't endothermic or exothermic, either. Explain that!? If you want to make it even more difficult, explain why salt doesn't dissolve in all solvents. If entropy alone was a force for dissolving, then everything would dissolve! There must be more fundamental rules or laws that govern the flow of energy, they tell us what is possible and what isn't.

[@sneakypress]

You need to study some chemistry ; then you will be able find the answers to your questions . There are rather simple CHEMICAL principles behind what you are asking . These explanations are not ‘ physics ‘ , they are CHEMISTRY . This video is good , but it is what you would expect from a physicist , and most physicists do not know much about the SCIENCE of CHEMISTRY .

[@viniciussantos14]

9:58 a lot of elements are named niobium in this periodic table Nice channel btw

[@4pharaoh]

Watching a video on entropy is like watching a football game where the goal posts are on wheels. Every time the decreased entropy is about to make a point, they shout “score another one for increased entropy” as the posts are pushed out of the way.

[@thedeemon]

The part about entropy and how it leads to higher energy states deserves a more thorough explanation. Another video maybe?

[@LQhristian]

Great video!!

[@richardsylvanus2717]

I'm watching this video naked

[@ArvinAsh]

Thanks for letting me know. I will let my team know!

[@watamatafoyu]

I will now get naked.

[@JimmyNeutronInThisHo]

Dawg I’m just trying to review😭

[@uninspired3583]

I'm having an exothermic reaction

[@vishalmishra3046]

Why is Schrodinger equation never solved for non-Hydrogen atom ? What if atomic orbitals of larger atoms turn out to be very different from what we know based on Hydrogen atom ?

[@ArvinAsh]

The solution gets too complex with increasing number of electrons because you have to account for all interactions - 3N dimensions, N being the number of electrons. This become intractable for even a small number of electrons. Approximate solutions however, have been carried out.

[@matssimmermacher3381]

One should perhaps add that the Schrödinger equation can be solved for non-hydrogen-like atoms, just not analytically. For atoms up to neon, numerical techniques allow for an essentially exact solution of the Schrödinger equation. Moreover, for atoms with more than one electron, orbitals are just building blocks that we use to construct and visualise the total many-electron wavefunction of the system. They are not unique and do not exist independently. Hence, such orbitals are indeed quite different than orbitals of the hydrogen atom. But that's not a problem. It is just an aspect of many-particle quantum mechanics and accounted for in the calculations.

[@alfadog67]

Chemistry for physicists!! Thank you Professor Ash!

[@mehran528]

Its all in my highschool syllabus

[@chronos826]

Great video

[@JohannY3]

Great explanation, thanks.

[@mcbaggins12]

This is the one video where I finally knew everything

[@Iancreed8592]

Cool theory bro. I love sci-fi

[@robertteh3056]

Basic questions need to be answered such as where do gravity, quantum loops, particles, quarks, bosons, electrons get their elemental force from ?

[@captainzappbrannagan]

Great video my friend! I always had the impression that the big bang started only with fields and photons, they were pushed with so much energy that they stabilized themselves as to not go faster than light by creating the building blocks of matter. Is this wrong? Thanks!

[@ExistenceUniversity]

Great question!

[@Timepass-mz7nk]

1:06 he is being realistic about high school where students are bored

[@GroovyLynx]

This is first semester in bsc physics/chemistry stuff

[@Science4Real]

quantum nature is like trying to understand how a cat can be both alive and dead at the same time without needing a morning coffee

[@mikemarsports]

Thank u for adding Chinese subtitles ❤

[@Serezin234]

Thank you for your video sir

[@davidfuller581]

Honestly the part that blew my mind most is that cold packs use ammonium nitrate. That sounds marginally dangerous.

[@parttimeuber865]

Typo at 7:17. Not methane... should be oxygen

[@carlstanland5333]

Just had a “Mitochondria is the powerhouse of the cell” flashback.

[@diaaelsaigh9746]

Loved it..

[@Scivinfacts]

Sir please make video on how schrodinger equation came ,and how it tells about particle positions, I am very confused about this ❤

[@phoule76]

I like being called his friend at the end of his vids.

[@shanewilson1160]

Can ionic bonding be explained completely via the Schrodinger Equation?

[@ArvinAsh]

Much of it yes, but I would not say all. But all of it can be explained inf you include other quantum mechanics principles and equations.

[@ManyHeavens42]

Yeah but what is the primary force causing all this reactions, I believe it's Hydrogen, hydrogen is the master key, and Dark energy that's another master key, hydrogen breaks down everything even the human body.

[@apollo-r5z]

Two electrons could be at the same place and time, but they would enter another dimension, temporarily neutralizing one another (excluding one another) because of their up spin and downspin cancelling one another.

[@scarletevans4474]

How many times smaller would atoms be, if we replaced electrons with muons or taus?

[@jlpsinde]

So good

[@UlfatMajeed-sn3kr]

Sir plz start live video with your viewers

[@michaelharmata6361]

This IS freshman chemistry.

[@nielsmadsen2185]

Please explain energy at the quantum scale. How does energy emerge+

[@hafizeolmezolmez6942]

Thanks but you can also cite for energy formation about subatomic energy fill configuration via "ss ps dps fdps" spin of subatomic orbital shells filling anyway in order to gain noble gase form of Quantum states of atoms

[@TedToal_TedToal]

Thanks, very interesting, enlightening, and intriguing video. I'm thinking about how the Schroedinger equation is in some sense a probability equation, and entropy is about probability too, about the most probable states of the system. I'm wondering why quantum mechanics doesn't somehow incorporate entropy into the schroedinger equation to produce a new and more complete equation?

[@thedeemon]

There is a certain notion and a formula of quantum mechanical entropy, see en.wikipedia.org/wiki/Von_Neumann_entropy However Schroedinger equation already works very well and is logically complete, adding something related to it won't make it "more complete", it will just make it incorrect.

[@sunergi]

I want to know why each orbital can only accommodate a certain number of electrons, despite having negligible mass

[@thedeemon]

Each stable solution of Schroedinger equation is a certain quantum state or a set of states. Each orbital defines a finite set of quantum states for the electrons, and Pauli principle doesn't let more electrons occupy these states.

[@Scinerd09]

Because each electron can have one spin (+1/2 or-1/2). This spin number is the spin quantum number of an electron and by Pauli’s exclusion principle no two electrons can have same numbers all the four corresponding quantum numbers.

[@jssamp4442]

I don't think ice melting counts as a chemical reaction. That takes more than just a transfer of energy. Ice melting is a physical reaction, a phase change. A chemical reaction involves reactants and products. You end up with different substance when it is done.

[@ArvinAsh]

It's true that ice melting is a phase change, but at the molecular level, it involves breaking and forming bonds between water molecules, which is an endothermic chemical process.

[@mdderrek9280]

This answered a big question i had since a while, thanks Arvin!!!!! But i see in 9:45 the energy level shell has Eight electrons despite it is only allowed Two of them, could you please explain that?

[@alexalekos]

but what determines if the energy in an exothermir reaction is released as heat or sound or anything else?

[@Michelle-e7j8c]

Question: At minute 8:16 we see that only two electrons (one spin up and one spin down) can occupy the same orbital. Then, at minute 9:30, we're seeing 8 electrons that are pictured as occupying the same orbitals (two on the innermost but 8 on the outer orbitals). Is this a conflict or is something else missing from the diagrams? I notice that pairs of electrons are grouped together in the outer orbitals.... Thanks in advance for clarification.

[@zacox]

This is an overly a simplified orbital structure. The H atom has only a spherical s-orbital that holds 2 electrons. While the O atom has that spherical s-orbital and “p-orbitals” along each axis (x, y, z). Only 2 electrons can occupy each of those three axial orbitals. So oxygen can have a total of 4 electron pairs that do not have overlap.

[@paxwebb]

Shells and orbitals are not the same. If we define n as the energy level away from the nucleus, then: n = 1 (K shell): 1 orbital (1s) n = 2 (L shell): 4 orbitals (1s, 2s, 2p) n = 3 (M shell): 9 orbitals (1s, 2s, 2p, 3s, 3p, 3d) n = 4 (N shell): 16 orbitals (1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f)

[@ArvinAsh]

Great question! Typically all the suborbitals are not depicted for larger molecules, for simplicity of illustration. See answers from @paxwebb.

[@Michelle-e7j8c]

@@ArvinAsh AhA! Thanks Zacox, Paxwebb & Arvin! Of course I had to look up electron orbitals, but I think I'm getting it now.

[@DrDeuteron]

Orbital Angular momentum quantum number. L = 0, 1, …, N-1 Then azimuthal quantum number, aka projection of L on an axis. M = -L, L+1, …, L- 1, L

[@AndyCutright]

You jump from one slide saying identical electrons cannot exist in a single orbit and then say orbits can contain multiple electrons. I'm not feeling like you explained the Pauli exclusion principle properly.

[@matssimmermacher3381]

That only applies to electrons with the same spin. Electrons with opposite spins can still share the same orbital angular momentum and coincide in space. Arvin explained that briefly but properly here.

[@AndyCutright]

@@matssimmermacher3381 Electrons have two types of spins. So with three electrons in one orbit, for instance, two of them have to share the same spin. Which Ash said isn't possible. Ash did not mention anything about angular momentum.

[@matssimmermacher3381]

​@@AndyCutrightYou are probably confusing a shell that can contain more than two electrons with a spatial orbital that can indeed contain two electrons at most. Take the second shell of neon. It contains eight electrons in four spatial orbitals (one 2s and three 2p orbitals). Not all eight electrons in the shell share the same orbital angular momentum and thus obey the Pauli principle.

[@clarencegreen3071]

As a young fellow on a farm in the hills of east Tennessee, we would dissolve ammonium nitrate (fertilizer) in water for application to various plant beds. I observed that the mixture got really cold, which I thought was very strange. I didn't understand it then, and I'm not so sure I understand it even now. Cold implies slower-moving molecules. What slows them down?

[@chriskennedy2846]

Imagine a very bizarre game of pool where all 15 balls are racked and put together in the familiar triangle shape at one end of the pool table. But this time instead of one person hitting one cueball at the group of balls to "break" there are already about 20 cueballs randomly buzzing across the table in every direction at a fixed speed. Then right after the racked 15 balls are inserter onto the pool table, the 20 cueballs start running into the triangular shaped group of balls and eventually cause the organized group of 15 balls to scatter all over the pool table. Two things happen. The 15 balls that were originally motionless acquired a velocity so that they could all scatter in one direction or the other. The cueballs that did the striking lent some of their energy to send the 15 balls into motion, and as a result, the cueballs were slowed down from their original pre-break velocity. The billiard balls' gain was at the expense of the cueballs' loss. The organized group of 15 billiard balls is like the ammonium nitrate dissolving in water (separating into ions in this case) , and the sea of random cueballs moving about the table are like the water molecules. Since temperature is actually a measure of the individual kinetic energy (velocity) of the molecules, the velocity of the surrounding water molecules experience a reduction in velocity, which we feel as a drop in temperature.

[@zacox]

The billiard ball analogy doesn’t quite explain the phenomenon. Consider dissolving calcium chloride (like in an instant hot pack) where the same action of water molecules banging into a solid salt occurs but the temperature increases instead of decreasing.

[@chriskennedy2846]

@@zacox It's a pretty good analogy to help understand the temperature drop in the solution, but I agree, it's not complete. Of course I could have also added the fact that there are more combinations of ions mixed with water than there are combinations of recrystallizing, so entropy within the temperature range of the reaction plays an obvious role in the spontaneous reaction too. However, I didn't want to write a book, so I limited my focus the the NH4NO3 borrowing energy from the H2O energy. Calcium Chloride by contrast generates heat because the Calcium and Chloride ions needed to steal some energy to break free but then they generate more energy than that when they attach to the H2O molecules in solution. (Which doesn't happen when the NH4 + and NO3 - attach to H2O.) This Ca 2+ / Cl -1 transfer creates an overall increase in kinetic energy of the solution. By the way - this is similar to what happens to ATP. Most biology students are taught an oversimplification with the statement: "Living things get energy from ATP when the bond between two of the phosphates breaks and forms ADP + P." But in reality, that is the step that costs energy because the bond needs to be broken, but the energy return when the P (phosphate) attaches to H2O is more than the initial investment - so it is an energy profit that is utilized by living things. Of course a third example is something that is hardly soluble at all in H2O such as Silver Chloride. In that case the first step (breaking apart the Ag from the Cl) is rarely achieved so it doesn't have a chance to be exothermic or endothermic because the second step is also rarely achieved.

[@jonathanl8538]

0:09 Ice melting is NOT a "chemical reaction".

[@richp6716]

Best of luck in your apricot business 😁

[@stephenzhao5809]

12:48 ... overall energy is not lowered, so how can this reaction occur in the first place? Well, this is where the second law of thermodynamics links up with quantum mechanics. While minimizing energy is a key concept of physics, we also have to consider entropy of the system as a whole. Nature tends to favor processes that increase entropy in the universe, or its oversimplified description, increasing disorder and scattering. ❤Even if a reaction absorbs energy, 👉if it increases overall entropy, it can still drive a reaction. 13:17 So while breaking the bonds between the ammonium and nitrate takes more energy than is released when the ammonium and nitrate ions dissolved in wather, it is more than made up by the increase in entropy or disorder that results from the breakdown of the crystal lattice of the ammonium nitrate. To sum it up: exothermic reactions release energy, making their surroundings warmer, while endothermic reactions absorb energy, cooling their surroundings. The driving force behind both these reactions is the balance between the energy state of electrons in the molecules and entropy. The requires a more nuanced understanding beyond simple quantum models like the Schrodinger equation of a hydrogen atom. Understanding the physics behind these reactions shows us the chemical reactions aren't just about molecules colliding - they're about energy transfer, obeying the laws of quantum mechanics and thermodynaics. So whether it's the crackle of a fire or the chill of an ice pack, it's all about the flow of energy, which is ultimately all about physics. See you in the next video my friend!

[@gracemember101]

Does an endothermic result from a lowered energy density rather than an actual creation of new compounds? I noticed that the solid was dissolved in water but remained intact chemically.

[@straef9002]

4:51 Schro-WHAT.

[@hakiza-technologyltd.8198]

Great

[@OBGynKenobi]

Wait, are you saying that Schrodinger's equation is a langrangian?

[@gshort4707]

Brilliant explanation. Wish I was taught this at school.