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hello and welcome to technically speaking a podcast where scientists and engineers come together to chat about common interest share knowledge and satisfy some curiosity i'm Laura and in this episode i'm joined by Ghinwa, Emma and Antonia talk about thermodynamics and try and figure out how it links to our different disciplines in science and engineering
and why it's useful. Ghinwa kind of started off this conversation just two of us originally last week so what do you find so interesting about thermodynamics?
Well the first time i encountered thermodynamics was in my bachelor degree i did chemistry and i studied basic and advanced thermodynamics and even though it was really hard to grasp you know the concepts at the time and i still find it really hard but at least i was initiated to the importance of thermodynamics and any physical or chemical process that involve a change of energy and i think it can complement other you know scientific topic to understand how the world evolved from the big bang
till now it can explain reactions uh you know that can constitute the process of life whether in nature or in our bodies you know telling us why this system evolves this way they took this path and not the other so that's what makes me really interested in thermodynamics so basically it explains life the arrow of time yeah why things are evolving this way and not the other way cool i guess we'll get into more of the details as we go through this conversation because there was a
load of technical stuff in there um and i have to confess that i have never actually been taught thermodynamics so i think you know more about it than i do i agree it's very hard um i kind of picked it up as i've gone through my career Emma your background is in physics so i'm guessing you can help understand it from a different point of view yeah i hope so at least anyways when i was first introduced into thermodynamics it was in the concept of the definitions of
thermodynamic laws and kind of some basic concepts which didn't seem to have much applications but um then in like later study we looked at it from a statistical mechanics background and that kind of just like flipped a lot of switches to me to how things are actually important and how entropy i understood what entropy was in statistical mechanics when i don't think i really knew what it was in the context of thermodynamics so even with the thermodynamic laws you
kind of just learn them as a statement but you can get a lot of insight into what they actually represent and do for example the second law of thermodynamics is about how you can't have a decrease in entropy but that can actually evolve to how you can't have heat movement from cooler to hotter but when you can learn about more interesting applications and what they represent with the zeroth law of thermodynamics which is that when you have two bodies which are in thermal
equilibrium with a separate third body if you change the temperature of that third body you can use how the other two bodies react to rank their temperature and you can scale that based on the volume of an ideal gas and that's where you get your absolute temperature kind of um thermometer and you have absolute zero being the lowest temperature it allows you to kind of rank bodies by temperature which is essentially what we do with thermometers so to understand the basic laws of
thermodynamics you've studied something even harder with statistics to get the inverted commas basics down yeah in the basics it's a lot of seeing an equation you've never seen before and then trying to make sense of it and they feel like the sense sometimes comes with the harder stuff because you understand some hard stuff and then it makes it look easy even though it's still a difficult concept to grasp i feel like it makes it a lot nicer when you can go back to some more simple
stuff and you have a reason to why it's important because you've got your head around we'll start to get your head around that more difficult thing i suppose it makes the stuff that first seemed hard it's even be easier it's kind of my understanding of trying to teach myself some of this stuff and so on here your background's different again so tell us something that you know or that you find interesting or how you got into thermodynamics i studied chemical engineering so thermodynamics
has to have an application but for the first two years of my undergrad it did not have much of an application so how emma was talking about the laws of thermodynamics i was like okay that exists i don't know how to use that yet but it exists and we had to learn all these concepts to get to the point of this is how a basic engine works the basics of how a gas turbine cycle works and how refrigerators work i guess that relates back to how now the uk is looking at heat pumps to
help decarbonize heat through basically changing from our gas boiler system to kind of reverse air conditioners thermodynamics is basically about moving heat around is what that word literally means that's what you're talking about with air conditioners and heat pumps they move heat from one location to another i remember reading about this a while ago when i was trying to get my head around thermodynamics near the start of this textbook after it talked about the crazy stuff that happened when
they were trying to figure out thermometers as emma mentioned was this is how refrigerators work which again is about moving heat around and because we have refrigerators that meant that cities could expand because you could be further away from food because now food would last longer because it's refrigerated so thermodynamics had this very profound effect on how people lived and where they lived which i think is quite a powerful statement that suggests that we should look into
how thermodynamics works in a bit more detail so i'm guessing that someone here can explain in more detail how a refrigerator actually works beyond it just moves heat around all right let's give it a go the basic idea you have an area you want cold an area you want hot and in it we'll use a working fluid and that will sort of be the medium for transferring the heat between places and i'm gonna get a diagram so i can like talk through this in order so your goal is to get a diagram from
the internet whatever she finds we will share as a link for this episode i hope it's a good one otherwise um otherwise this this explanation will be really bad i know that refrigerators have compressors my freezer is not particularly expensive when you can hear the compressor kicking in it's quite loud and there's like oh i like a what's the best way of describing it i want it's just like a radiator like a a network of pipes on the back like a coal it is a radiator you know the back of
your fridge there's a black finned metal and that's where it lets out all the heat because you've got um now i need to remember which way around this is i think we can relate refrigerators to the second law of thermodynamics that says that heat will never go spontaneously from cold places to warm places so it needs to go from the warm meat and food we put in the fridge towards the cold fluid that we have on the back of our refrigerator and it works by i think compressing
decompressing that refrigerant because just imagine the refrigerant is in um as in a container whenever you compress it then you increase the temperature but then it circulates in kind of a tube and then there's a decompressor that kind of vaporizes it so it becomes colder because it's just you know the the fluid it has a lot of room to move so it vaporize and become colder and this cold one is going to circulate and take the warm or the warmth from the food in our fridge
yeah so we're also missing the latent heat of evaporation or condensation basically when you're boiling water for example when you're at atmospheric pressure you can never get it above 100 because all the extra heat is going into evaporating the liquid changing state from liquid to vapor so all that energy goes into that and so when you condense it goes the other way the heat is lost that's very true it's actually related to evaporative cooling which is sweating
you know when the water evaporates from you know the skin is just take part of the latent heat from the water that remains on our skin so it cooled down and i think this is the same thing that is happy with the coolant or refrigerant in the refrigerator when it evaporates this is what you mean antonio don't you well trying to say yes [Laughter] so you're saying that the substance that's in the cooling loop because it's either a liquid or a gas depending on where it is
when it's in the part of the loop that's inside the refrigeration chamber then it's being turned into a gas because it's taking heat out of that chamber and then when it goes to that snakey coil on the back of the fridge it's turning back into a liquid that right yes right the diagram i'm looking at confused me because it was blue on the hot side diagram didn't work well for you antonio therefore we are not sharing that diagram in this podcast episode description we shall find a better one
you know though i feel like after all this time i understand latent heat now and i never really understood what was going on with it so that's a positive just remember when you eat boiled potato it has a very high latent heat that's why you're burned with it and it didn't doesn't like cool down very easily but it's not the same because you're not changing the state of the potato are you no it'd be a latin heat of potato rather latent heat of evaporation or condensing
i thought the latent heat is the energy stored in whatever that material and you're taking a part of it while evaporating because you're changing state from liquid to gas but i'm not sure honestly the energy that's stored is the heat capacity isn't it yeah i would say stored as heat capacity and then latent heat is the change of state yeah your explanation of sweating i think was correct because that's how i understand it but i think for a potato being hot because you're right certain
foods do feel hotter when they've been heated for the same amount of time yeah let's check latent heat this is not where i expected this conversation to go talking about the latent heat of potatoes but it's quite entertaining there may be dynamic food is the most important part of this of course then you know what order to eat things in so you don't burn your mouth you need to write the specific capacity of different food items you know which way to eat it but wouldn't we just look
at the surface area instead which has more of an effect the surface area like broccoli you know if you look at the stem versus the florets luckily it's not all that hot anyway though regardless of which part of it you look at from what i remember i feel like we're getting a bit off top very much off topic and please the latent heat you were right am i the heat required to evaporate to change face i think we might circle back to this if we start talking about some chemistry
in guinea you talked about thermodynamics in your sort of chemistry background so do you want to take us through some of that chemistry stuff that you know yeah so the way i understand thermodynamics as a chemist is when i talk about gibbs free energy and how likely the reaction is happening or how spontaneous or not spontaneous it is and i really like the gibbs energy kind of concept because it includes all the other state functions like the enthalpy the enthalpy and also the
temperature and the pressure without going into you know details of equations we always stand as chemists to calculate the gibbs free energy just to know if the reaction is spontaneous or not so we're talking about entropy always goes in a particular direction but then that suggests that everything is just trying to become more random like everything's losing its structure and all the atoms just spreading out into this soup of nothingness but that doesn't always happen because you get things
spontaneously ordering in nature isn't that to do with the gibbs free energy it's a complex topic to discuss but from my understanding of the gibbs free energy you have a competing factors of the enthalpy which is the heat in whatever system you have and you have then the temperature and the enthalpy so the higher the temperature and the higher the entropy the more the system is spontaneous and the more the gibbs energy is negative but also if the system has a lot of
enthalpy which is uh like the heat content in the system then this would outweight the enthalpy and then the gibbs free energy will become positive so the gibbs free energy is essentially the change in enthalpy minus change in entropy at a particular temperature right yes and that's why you talk about it being positive or negative because it's the difference between the two and the fact there's temperature in there means it's temperature dependent which i guess is why you get some
chemical reactions happening at certain temperatures yeah so sometimes you need to heat something up to get a chemical reaction happening yes basically they make you work for it it's nice we haven't really discussed work yet in the context of thermodynamics do you want to explain now you're talking about endothermic and exothermic reactions it's a reaction that needs heat to happen and a reaction that you know release heat when it happens so here's an interesting example of a exothermic
reaction which is aerobic respiration it happens for free so that's respiration in the presence of oxygen how does that happen for free explain this is a very complicated process there's a lot of steps this was a bad example i wish i was an easier example okay so so far your contribution to this is looking up things that aren't very useful oh pretty much but you're keeping us all on track though you're letting us know when we're saying something utterly stupid i think
which i think is going to happen quite a lot because as we're saying this is quite a difficult topic to get your head around yeah i have an example that explain this balance between the heat supply to the system and the enthalpy and the temperature which is i think we all use on our daily life it's boiling eggs the conversion of liquid egg to a solid egg while boiling it you can explain it thermodynamically because the major component of the egg white is a protein and i cannot say the
name of it because i cannot spell it but then it is held in a compact and ordered and structured kind of way and this structure is held by hydrogen bonds but then to break these bonds actually we supply heat yeah so that's why we put it on the hub with water and then when we supply heat we are increasing the enthalpy so if enthalpy is positive then delta g is positive then the process is not spontaneous then we can reverse it however at a temperature above the boiling point of
water which is 100 degrees the term t times delta s which is the enthalpy times the temperature outweight delta h and delta g then become negative and therefore the egg is boiled and you can never reverse the process from boiled egg to just you know white blues egg okay so that's because of the way the entropy that delta s term changed yes because it seems at high temperature above 100 degree you are breaking these h bonding and you are increasing the randomness of the egg white
protein and therefore that ice is increasing and the temperature is high therefore this term from the gibbs free energy is higher than the heat supply to the system gibbs energy then is negative and therefore this process becomes spontaneous and irreversible okay that's quite a good um real-life explanation of why gibbs free energy is so useful to understand i think we're back in food again as well which i like don't cook your eggs if you don't want cooked eggs
this is gonna take another really quick turn so i'm gonna change the topic so much for keeping us on track it's how this podcast goes it's always a bit i was gonna say a bit random that's a terrible pun a bit full of entropy so i'm gonna change topic we like film references or movie references in this podcast and in the avengers captain america has a shield that absorbs all vibration i don't think that's possible i know it's a film so they don't have to have
things that are physically possible but if something were to absorb vibration all vibrations what would that mean well if i had to speculate and it is speculate i would say that the shield would have to be very very heavy and very dense because i would imagine it to be like a two body system where you have one like bigger mass is stationary and then you have a lighter mass which is moving that collides with the stationary mass and then the lighter mass completely changes its momentum or
can come to a halt but the stationary mass doesn't actually change physically and so if in this scenario we're imagining that the shield is the stationary mass i think i can i guess conceptualize it there but i also do think maybe it's me getting a bit confused with the whole thor's hammer being very very heavy but i think they're very similar though i swear there's something about the fact that they're similar so maybe physically they're similar i then think we have a
three-body system because there's a thing hitting the shield and there's captain america holding the sheep so is captain america the more burden or is he better absorbing it is captain america absorbing all of the momentum or is the shield absorbing it the shield is yeah the shield is so as long as the person holding it is strong enough to hold it up yeah they don't have to also withstand the force of something hitting it that's what the shield does so captain america is just
a stand in that case he could be an inanimate object wouldn't matter it doesn't have to be a person i think it helps that he's a superhero though does maybe him and the shield form one system and they are the big mass they want to be a stoppable force yeah yeah but then another though like the shield by itself can do stuff i guess but captain america by himself can do stuff as well but like when they're both together it's like the strongest so if between captain america and his shield
they keep absorbing all this vibrational energy what are they doing with it how are they storing it thermodynamics is just the transfer of heat or the transfer of energy so if all this energy is being transferred to them what happens to it and we know that energy cannot be created or destroyed only transformed unless you have equals mc squared but i don't think we're creating any mess yeah you'd be creating must inside them maybe that's how captain america feeds that's what i wanted to
say laura when i was like no maybe he doesn't eat actually have you spotted him eating at any time it has the shawarma at the end oh shield is just a conduit for him to get energy and not have to eat food that's what we're going with we're back to food again oh i've tend towards food not towards randomness you mentioned that you do chemistry and there's a lot of thermodynamics in it and i think you you're also using in your current job right do you want to take us back onto more sensible topics
yeah i think i'm i'm going to take it here very seriously uh back to siri discussion so yes as a reactor chemistry modeler one of the very useful aspects of thermodynamics that we use in thermodynamics modeling which is used to predict chemical speciations and properties at conditions that are impossible to measure in laboratory for example if you talk about the pressurized water reactor that are used in the nuclear power plants and they are by the way the basic model for the new uk smr
that we are all looking forward to see them emerging in the near future so thermodynamics is a really essential part of their design so the pwr operate in very special conditions so we're talking about hydrothermal regimes and temperature between 100 and 350 degrees and we have there the water and we have you know the presence of radioactive materials of moderators that can be like acids other electrolytes you know are there and we have also the the vessel itself
which is you know a kind of metal or metal alloy so we we are expecting a lot of reactions that may be happening in the in the reactor and the thermodynamic allow us to understand these chemical reactions that might happen if we don't understand these actually that might lead to different complications for example a fatigue or corrosions of the metal or like drop of efficiency in the you know in the reactor itself so with the thermodynamic we can infer from reactions happening at let's say
standard conditions or laboratory conditions and then extrapolate them to predict uh conditions and thermodynamics entry at higher temperature and this is really complicated to explain and i don't understand it myself even but i know that people spend like 20 30 years of their life trying just to derive entries for chemical species that are present in the pwr that no one can understand until till that moment so that's what i do at the moment in my role but i'm really very new to that so
yeah but i'm quite excited to learn more about it but that sort of illustrates how useful thermodynamics is that you can take something that you've done in a laboratory and then extrapolate from that to more extreme conditions but that's interesting because basically we've gone from like the theoretical gibbs free energy figuring out what reactions are going to happen spontaneously and all that and people working in your area are able to actually predict chemical reactions and whether or not
they would happen without having to experimentally do all of them and find out all of the options yeah it is very simply explained but it is really very complicated yeah you said there's a lot of materials a lot of different chemicals in there and there's radiation as well which does all sorts of wild things yeah exactly and there's also some deposit that they call crud but they don't know actually what these materials are because whenever they want to understand
or replicate that in a lab you know the whole operating conditions change and these materials their solubility might uh defer or the reactivity might be fair and then they would have totally different different results from that i think pressurized water reactors have been around for a fair while and the uk's got like 60 years experience of operating nuclear reactors is an awful lot that we know about them but it's interesting to see that there is still more to find out and it's more about
those finer details that thermodynamics can help us look at you would decide then about the design of the pwr to make it more the more efficient or less complicated chemically for example by choosing a different moderator would change what chemical reactions would happen inside the pwr one thing that impresses me is you talked about chemical reactions happening which obviously is quite a small scale thing and then scaling up all the way to these really big
reactors that are bigger than a building needs to be bigger than my house and then a different length scale again is what i was doing in my phd which is what emma mentioned which is like statistical mechanics so i understand that as a very simple definition is that it's sort of a description of physical systems and where the atoms are sitting in that system and what momentum they have so it that's an even smaller that's beyond chemical reactions this is what the actual atoms are doing and
thermodynamics can encompass all of that yeah because uh with statistical mechanics as i said it kind of what everything together for me because it looks basically probabilities and how the probabilities of a system determine what the average energy is going to be what the average number of particles is going to be for magnetization what their magnetization could be with large systems statistical mechanics is following the second law of thermodynamics in that the entropy is
always going to evolve to a system with maximum entropy so essentially maximum disorder entropy is very related to um order and disorder in a system and so that's what statistical mechanics is uh kind of governing i'd say it's very like probability based which can be a bit scary but it's it really is nice sometimes to think about the bigger picture of things rather than just think about specific heat transfers to different places if you can look at things from a very broad view
it can help you understand how entropy changes occur and uh when you're moving into this state of disorder it's really intriguing because i saw in um in a film in 2020 that came out tenet i didn't know if it was just movie magic at the start but they mentioned entropy and they said that um it's all about inversion and things moving backwards in time and so the idea is that they have like a bullet which moves backwards in time and so it's entropy decreases as we view it but not to get
to physics and talk about inertial frames but in the bullet's own inertial frame its entropy is increasing which is allowed and that is moving backwards in time but we're viewing it as this bullet which is decreasing entropy which is supposedly impossible through the laws of probability and statistical mechanics you can't have something that decreases entropy but if it's moving backwards in its own inertial frame apparently you can intend it anyways basically it's based around the second law of
thermodynamics being broken but also not necessarily broken if you're in the right inertial frame which is why the film is kind of confusing and i was like thinking i was really smart because i understood what entropy meant but the film is very confusing so it doesn't actually help much but it's um it's just about how important changes to physics such as how the second law of dominant acts being broken is it even possible that i could leave to inversion and people moving backwards in
time because i was like i don't even know because entropy is such a huge kind of concept i don't know if entropy could decrease if it would lead to people moving backwards in time but maybe maybe tennis is what we need to base our textbooks on in the future yeah see and i was trying to read up on statistical mechanics in preparation for this episode um i came across a textbook that's online from stanford university i think and they mentioned this and they said that the second law of the dynamics
entropy can only go in a certain direction it's only really theoretical and it's not really a law so much as a definition and it you're right it depends on your reference point so because we're used to time moving a certain way an example could be that if i break the window that i'm sitting next to that window isn't spontaneously going to put itself back together and i understand that intuitively but if we looked at the world in a different way entropy might be different therefore time
might run different i don't think that's really how it was used in the film people did they go through some sort of device to invert entropy the device was the thing that i think made it a bit a bit less scientific the fact that there was a device that somebody goes through and they do like one revolution of this like turn-in device and automatically their entropy is decreasing they're moving backwards in time that was a bit of movie magic i don't think there's a
device which can decrease your entropy uh especially something that was just so like it just looked like a lift we uh we learned the specific fact that when we're doing about these like huge laws of probability with the entropy having to go in one direction was that if you have a very very small system you can actually have this decrease in entropy which is kind of like freaky but obviously in any given system you have so many atoms and so many states that you're never going to
observe this decrease with moving forward in time as well i just made me think about anti-particles and how i think it was feynman theorized anti-particles as particles moving backwards in time and we've kind of like accepted the concept of anti-particles moving backwards in time as this fact so like if we've accepted the anti-particles and particles moving backwards in time maybe entropy decreasing isn't so crazy i don't know it's one of those things it's all about probability and it's
quite difficult to get your head around all the details of especially if you're someone like me that doesn't like just looking at equations on the page i like words so i think having these discussions is quite useful to helping understand these different concepts and i think the different points of view here have been really useful so we've got a chemical engineer chemist a physicist and i do random things i guess take my my phd was in computational chemistry so let's use that as my background
so i think this is probably quite a good place to end the conversation so having covered a range of stuff including lots of food related terrible puns and talking about captain america in movies that don't make much sense i guess from what you were saying emma yeah using some quite difficult to understand physical definitions all this strange complicated math is also really useful for society we're talking about refrigeration that changed cities and now we're talking about using heat pumps to
decarbonize how we heat our homes by using electricity to move heat around rather than just burning gas so there's probably quite a lot more that thermodynamics can do for us i suppose if what we said hasn't made any sense please feel free to tell us if you want us to clarify anything also ask you can email us you can find us on twitter and we are also on instagram the views expressed in this podcast belong entirely to the person that said them they do not represent any industry
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