The First & Zeroth Laws of Thermodynamics: Crash Course Engineering #9

The First & Zeroth Laws of Thermodynamics: Crash Course Engineering #9

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Whether you’re putting food into your body
or fuel into your car, you’re always trying to get
something out of raw materials. You’re trying to convert energy. But if you want to understand how this works,
we need to talk about thermodynamics, and the
laws behind it. Only then can we truly harness the power of
energy as engineers. [Theme Music] Energy is constantly being converted all around
you. When you take a bite of an apple, you
take in the fruit’s energy and convert it into
something that your body can use. Maybe you’ll use it to help power the marathon
you’re training for. Maybe it’ll go to power your normal bodily
functions. Or you might store the energy to use later,
as fat. But energy conversions don’t just happen
on a personal scale. They’re also at the core of many engineering
designs, like with hydroelectric dams. In a hydroelectric dam, water turns a turbine, which then
turns a metal shaft in an electric generator, converting
the movement of the water into electricity. These conversions are important, because
energy doesn’t just come out of nowhere. It needs to come from some other type of energy. So, to better understand how energy can be
converted, you need to understand thermodynamics. Thermodynamics is the branch of physics and
engineering that focuses on converting energy,
often in the form of heat and work. It describes how thermal energy is converted to
and from other forms of energy and also to work. And thermodynamics is one of the main focuses
of mechanical engineering. Because thermo, as it’s often called, is
critical to engines. Engineers need to know how much heat or work
they’ll get out of an engine if they put energy into it. We’ll talk a lot more about engines in the
next episode. Even when we’re not focused on heating or cooling
something, like with heat pumps and refrigerators,
we still don’t want our machines overheating. After all, engineering is not just about getting more of
what we want, but also controlling what we don’t want. It’s not just mechanical engineers that
deal with thermodynamics. It also plays a big role in chemical engineering. When chemical reactions form new compounds,
they often create energy. And often that energy is thermal energy. Now, to understand how all this works, we
should start at the bottom: the zeroth law
of thermodynamics! Yes, that’s really what it’s called! We only came to understand the zeroth law after its
more famous siblings – the first and second laws –
had already been established. But it was considered so fundamental to
thermodynamics that it was promoted to be
more than first – so, “zeroth”! Now, this law focuses on temperature and defines
thermal equilibrium. In general, an equilibrium is where certain
properties, like pressure, volume, or temperature,
remain the same across the system. So, if two or more things are in thermal equilibrium,
then they’re all at the same temperature. The zeroth law says that when two objects are
individually in thermal equilibrium with a third object,
then they are also in equilibrium with each other. This is important because when a body is left in a
medium at a different temperature, energy will be
transferred until a thermal equilibrium is established. That’s why, if you leave a cold soda out
in the sun, it will warm up and reach the
same temperature as the air outside. The basic ideas behind why this happens lie
within the next law, the first law of thermodynamics. The first law of thermodynamics applies the law
of conservation that we learned a few episodes
ago to thermodynamics. It basically defines heat as a form of energy,
which means it can neither be created nor
destroyed. So we can’t create or destroy energy, but
we can convert it from one form to another. This might seem pretty simple, but it’s
a powerful idea. It allows us to better understand a system, how
we can get energy from it, or how we can stop the
conversion of energy when we want to. Now, no matter what system you’re looking at,
there are two areas of energy that we need to
concern ourselves with: the energy contained within the system, and the
energy that can move between boundaries. Let’s start with the energy inside a system. We can break it down into three main parts. The first is kinetic energy. This is the type
of energy that’s involved with movement. The most common form is translational kinetic
energy, which is when something moves from
one location to another. There’s also rotational kinetic energy, when
something spins or rotates, and vibrational kinetic
energy, when something shakes or vibrates. Think about it in terms of throwing a baseball. As it flies through the air, the ball will
have kinetic energy. The kinetic energy would be translational
as it moves from your hand to your friend’s
mitt, and rotational as it spins in the air. The second type of energy inside a system
is potential energy. This is energy that can come from where something
is, even if it’s not moving. We can basically think of it as stored energy. Potential energy often has to do with how
high something is. The higher it is, the more potential energy
we can have. This is often called gravitational potential
energy. Like, if you’re climbing a ladder, you’ll have more
and more potential energy with every step you take. But potential energy can also come from an
object’s horizontal position. Think about a bow and arrow. Using elasticity, we can transfer potential
energy to an arrow as we draw it back in a bow. As we fire the arrow, the potential energy
will be transformed into kinetic energy. But the third type of energy that we’ll
find in a system is a bit different. It’s called internal energy. Internal energy is the energy associated with
the seemingly random movement of molecules. It’s similar to kinetic or potential energy,
but on a much smaller, microscopic scale. Take a glass of water for example. As it just sits there on a table, the water
doesn’t seem to be moving. But on a microscopic level, the water is
teeming with molecules that are traveling
around at super high speeds. While this type of energy might not seem as
important, it can have major effects on a system. That’s because changes in internal energy can result
in changes in temperature, changes in phase – like a
solid to a gas – or changes in chemical structure. All of these types of energy – kinetic,
potential, and internal – show us what can
exist within a system. But these types of energy can’t cross the
boundary from their system to the surroundings. But we’ve already talked about the main
types of energy that can cross boundaries. One is heat, which we know to be the flow of
thermal energy, and another other is work, which
is essentially any type of energy other than heat. So knowing all of these different types of energy
involved with a system can help us understand the
first law of thermodynamics. Let’s start with a closed system, where
no fluid is moving in or out. A good example would be a piston enclosed
in its cylinder. The first law of thermodynamics states that
the change in internal energy, kinetic energy,
and potential energy of a system is equal to the heat added to the system,
minus the work done by the system. This equation may look pretty complicated,
but there are a few different scenarios that
can help clear it up. One is a stationary system. If you look at the left side of the equation, you’ll
see that the changes in kinetic and potential
energies will be 0 for a system that isn’t moving. Another special case is an adiabatic process. An adiabatic process is when there is no heat
transfer. It’s rooted in the Greek word “adiabatos”,
meaning “not to be passed”. This can happen if there are no differing temperatures,
or if something is so well insulated that only a negligible
amount of heat can pass through the boundary. Think of it like how a good thermos bottle
can keep your hot chocolate warm. Now you can also simplify this equation if
you have an isochoric process. When a process is isochoric, the volume of
the system remains constant. This often means that there won’t be any
work, leaving us with only heat on the right
side of the equation. Any of these special cases help give you a
much simpler equation to work with, but this
all has to do with a closed system. Oftentimes you’ll find yourself dealing
with more complex, open systems. Unlike closed systems, open systems have a
flow going in and out. A good example would be if your basement flooded
and you wanted to pump the water out of it. With a system like this, you’ll need to
introduce a different energy measurement:
enthalpy. Enthalpy includes internal energy, but also
adds in the energy required to give a system
its volume and pressure. For an open system, you’ll also want to
refine what you mean by work. Here you’ll want to focus on shaft work,
which is basically any type of mechanical energy
other than what’s necessary for flow. Going back to our equation, you’ll want to replace
your internal energy with enthalpy and change your more
general work to focus specifically on shaft work. This will let you apply the law to open systems
as well. So let’s use a flooded basement as our open
system. First off, we should establish that we’ll be treating
the basement as our system and the outside, where
we want the water to go, as our surroundings. When we run the pump, it will take in electricity
and convert it to shaft work, which turns the pump. That energy will then be used to get the water
moving, which will change some of its potential
energy to kinetic energy. Hydroelectric dams are open systems too. If you think of the dam as a system and its
environment as its surroundings, then you see that there’s flow coming in, in the form
of water, and flow coming out in the form of electricity. It’s a little more complex than just draining
a basement, and it’ll take a lot longer to learn everything
that’s involved with generating electricity, but
the laws behind it are exactly the same. So you see, you can’t always find the exact
answers to problems quickly. But through science and engineering, you’ll
have the tools and knowledge to solve them
the best you can. So today we learned about thermodynamics and
how it shows up in our lives. We started by learning the zeroth law of
thermodynamics and what it means to reach
|a thermal equilibrium. Then we talked about the different types of
energies involved with a system and defined
the first law of thermodynamics. We also found out that stationary, adiabatic,
and isochoric processes can make our lives
as engineers a little easier. I’ll see you next time, when we’ll learn
about entropy and move on to the second law
of thermodynamics. Crash Course Engineering is produced in association
with PBS Digital Studios. You can head over to their channel to check
out a playlist of their amazing shows, like Brain Craft, Global Weirding with Katharine
Hayhoe, and Hot Mess. Crash Course is a Complexly production and this
episode was filmed in the Doctor Cheryl C. Kinney
Studio with the help of these wonderful people. And our amazing graphics team is Thought Cafe.

100 thoughts on “The First & Zeroth Laws of Thermodynamics: Crash Course Engineering #9

  • CrashCourse Post author

    Note from our Content Consultant: Different branches of engineering sometimes define the first law of thermodynamics differently, depending on how work is defined. Essentially, work released from a system might be defined as a positive value or a negative value, and thus the first law can be defined as either Q-W or Q+W. Both are acceptable forms, depending on how the system is defined! We chose to focus on only one definition here to limit the confusion.

  • rockinstrawberries Post author

    Man this reminds me of 2nd year uni

  • Abdallah Manasrah Post author

    I find that setting the replay speed to 1.25 helps much with viewing this series

    Good job everyone

  • sugan Channel Post author

    Disheartening to see little views and likes for such gold content but dressed up cat videos slaying million views.

  • David Conway Post author

    So sick you guys… UNSUBSCRIBED!

  • Nikos Ladas Post author

    "adi{A}batos" the intonation should go at the bracketed A (source:greek) 😉

  • 6alecapristrudel Post author

    Heat is known to be the most devout of Holy Mother Entropy's disciples.

  • Andrew Hamilton Post author

    Good god that, I want to say, bookcase is giving me anxiety

  • watbenikgoed Post author

    i hate how people misrepresent the 2nd law to explain how evolution is impossible. the earth is not a isolated system! ever heard of THE SUN?

  • Delivery McGee Post author

    Fun fact: matter is also a form of stored energy. That's why nukes work — a little bit of the, say, uranium atom is converted to energy when it decays — and why the masses of subatomic particles are measured in electrom volts. Also, heh heh, she said "shaft work."

  • Kun Feng Post author

    Sponsored by Ant man?

  • Penny Lane Post author

    Wow, this felt more than just a bit rushed.

  • rajivunome Post author

    Can you get a new narrator!!!!!!!!

  • Coreflake ! Post author

    To be fair. If you leave a can of soda out in the sun, it will heat up more than the air around it…

  • THE_KRAKEN Post author

    This is my Second favorite CrashCourse you guys (& gals) have ever done. (Saying something because my favorite CC is CC anatomy and physiology which has my favorite Science entertainer that I know of in it.

    The cat!)

    (ok maybe I lied about the cat being my favorite. But everything else in this comment is at least not a joke. I mean you can’t tell if I am lying. I mean This is the Internet and we’re communicating entirely through text which isn’t the most emotionally revealing medium. The most I can do to prove that I am not lying (within reason) is point out the lack of stuff to be gained form doing otherwise) Edit: in case you want to know who I’m talking about but are to lazy to try and figure it out. (I don’t blame you) I’m talking about Hank.

  • Dannyboyz Post author

    Thank you for destroying the Big Bang Theory.

  • Mars 3099 Post author

    Wait until school starts up again. The views will shoot up.

  • Jimmy Melonseed Post author

    Chemical reactions release energy stored in chemical bonds as heat. They do not “create” energy.

  • Chris Anseeuw Post author

    Does anyone know what software is used for the animations in these videos? Would love to know, thanks!

  • mocha 907 Post author

    Slight correction: chemical reactions do not Create energy, they release energy.

  • Naveera Post author

    i see ant man, i click

  • Cassandra Gray Post author

    …except for the Mongols.

  • Berly Tan Post author

    I have to watch this 5x because I'm a slow learner. Hahaha 4 more to go. The beauty of video is that I can replay it and no teacher will be exhausted.

  • Robert Palumbo Post author

    Roman siphoning circ 100 bce

  • axelasdf Post author

    If you leave a soda in the fridge, it'll get cold. If you leave it in the sun, depending on the can's ability to absorb energy from sunlight, it will match or exceed the ambient air temperature.

  • harshwardhan bijalwan Post author

    You talk fast…

  • 3TE Post author


  • Eric Nash Post author

    I giggled at "shaft work". I am 12.

  • Time To Thrive Post author

    I find in quite hilarious when people use the 1st law of thermodynamics as proof that calories in equals calories out.

  • julie Post author

    The background set up is messing with my mind. 😲😵😵😵

  • mohamed magdy Post author

    You teach thermodynamics better than my college professor 😂😂😂 to all new engineers around thermodynamics is like a belly dancer looks beautiful from the outside but ugly from the inside 😂

  • FaZe CrAzY626 Post author

    This wouldve been super helpful in high school. My teacher couldnt really explain this and the whole class confused by this. I totally get this now.

  • Shabbar Ali Asif Post author

    I Never Thought Physics Could Be So Interesting

  • Connor C Post author

    Thermodynamics is by far the least intuitive part of my Physics class work. Though I've struggled with, I'm glad I get it now. I hope you cover thermodynamic cycles!

  • gaminglittleshit Post author

    138th comment

  • Wrong Number Post author


  • Michael Szymanski Post author

    This video perfectly summarizes my entire first Thermodynamics class in my first year of Mechanical Engineering. Great work! Keep it up!

  • Bromoteknada Post author

    She is quite sexy. Oh and thermodynamics are cool also, i guess.

  • Thinker Post author

    Still I don't understand what enthalpy is?

  • Bird_Dog Post author

    The 3 laws of thermodynamics as I understand them:
    1. You can't win, you can at best break even.
    2. You can only break even at 0.
    3. You can't get down to 0.

    Also: The 4th law of thermodynamics: "Never attempt to explain the other 3 at a first date."

  • MalfunctionM1Ke Post author

    The Thermodynamic Diet: Chater One, eat less potential energy rhan your body will actually use over the day. Book complete.

  • Arjun Prasad Z Post author

    Masterpiece of science will come in next episode. The Entropy and Second law of thermodynamics.

  • A Ric Post author

    That was good. I need to watch it again though. The end had me say, huh?

  • Abiding Love Post author

    I look forward to Crash Course Linguistics. It's an incredibly amazing discipline.

  • Tom Rundell Post author

    Adiabatic process, otherwise known as the Gandalf Process

  • Blu Crystl Post author

    Best energy converters are photon transducers. They convert free energy to power my computer.

  • Number Eight or Nine? Post author

    Kids, you do have to take chemistry AND physics to be an engineer. Learning the math is super fun too…

  • buster only full screen mode captions on boss rush Post author

    that intro always makes me want to look outside; I swear something is backing up in the driveway every time

  • wholesalebuyerdeals Post author

    Ur so sexy!

  • TheTechnicalNirl Post author

    Yay loved it! Thank you!

  • Nathan Eric Dolloso Post author

    Please do something about Aerospace Engineering, Please!!

  • alter Herr Entspannt Post author

    Energy is stored in an "Arrow"? I think they meant energy is stored in the stretched string and the torque of the bow.

  • Jory Jones Post author

    My favorite is the second!

  • Ashish Gupta Post author

    when your mum keeps interrupting you

  • Richard Morton Post author

    Can you explain the offside law?

  • Shemsy Post author

    i prefer w to be positive and represent the work dont on the system but just a nitcpick

  • Davide Roversi Post author

    Hi, does anyone know what animation program is being used to create these animations? Thank you

  • Prathamesh Dinkar Post author

    Very nicely Explained! Waiting for 2nd Law….

  • Unthoughtof Post author

    I think this is gonna be really useful for me cuz I'm starting engineering next year

  • Ezekiel guardian of benditha Post author

    I love your intro

  • Alex Rossouw Post author

    "The Higher you get, the more potential energy you have"


  • Xx_boy ender_xX Post author

    she's a great teacher!! I love watching these videos!! this is my favorite series by crash course!!

  • Seth Taggs Post author

    Ahh energy…

  • EozTheNew Post author

    I've seen a few cases of the Zeroth Law of, in areas where a more fundamental law was discovered some time after the first law. What happens if, further down the line, you find an even more fundamental law?

  • Rodolfo Patino Post author

    Help guys!
    Why in an isochoric process (volume), WORK can be scratch out of the equation??

  • Hardik Siroha Post author

    As a kid whenever I didn't want to clean my room, used to say that "entropy is the law of nature".

  • Debellate Post author

    At 3:00, if you left the soda in the sun, couldn't it be hotter than the surrounding air?

  • bkraj26 Post author

    When are you going to upload entropy and second law of thermodynamics. Eagerly waiting….

  • Erin Clark Post author

    6:47 why did she take the negative sign with the q? Shouldn't it stay???

  • Udit Sharma Post author

    She is sexy, crush on teacher thing haha 😂😂

  • Tobi Carl Post author

    You guys are the best channel on YouTube! By far!

  • Oussama Chayoukh Post author

    Thank you a lot!

  • Cheezus Price Post author

    I’m applying most of my energy to Shaftwork

  • Seth Wagoner Post author

    so you are saying jet engines do not use fuel? and the engines use Thermodynamic? them rotten liars

  • Keke Lau Post author

    wonderful course that include a very broad introduction and framework about engineering .

  • Pedro Cruz Post author

    Well,the video is about to characteristics, explain about to the equilibrium the fluid try to be in the same temperature, explain the first law, explain the tipes of kinetic energy for example the translational, rotational,vibrational.Explain the heat formula and variants of that
    Pedro Antonio Reyes Cruz.

  • Confident A. Lpz Post author

    That's interesting, because we can see the laws of Thermodynamics in simple things that happens every day but we don't put attention to them. Like a future engineer I see this very important, some process or machines need to be understanding (Energy like heat, like electricity, etc.) and know how solve problems. Saludos. Brandon Adheo Aldana López. ENE04A.

  • HARI SCOTT Post author

    Hit or miss i guess they never miss

  • Dan Victor Post author

    Every engineering course sees this. It's basics.

  • Alex hernandez Post author

    This topic sounds interesting, as a future engineer is one of the basic fundamentals that we must know in order to apply to many functions Daniel Alejandro Hernández De La Torre ENE04A

  • Aldo Elizondo Post author

    This is an excellent introductory video to thermodynamics because it very simply explains things that, theoretically reading them, are a bit complex, but the girl no comment that the thermodynamics only work in a especifica moment of the time ( It worked with straight lines).

  • Jaqui López Post author

    This video is about:
    The first law of thermodynamics also known as Law of conservation of Energy, states that energy can’t be created or destroyed.
    And the second law states that the entropy of any isolated system always increases ( entropy is the measure thermal energy per unit of temperature)
    Jaqueline López UP170620

  • Jdege Post author

    Great explanation!

  • Luis Alejandro Ocegueda Ventura Post author

    First, we need to focus in the zeroth law, that represents the thermal equilibrium between objects those are sharing their heat one each other, and when other object with different temperature comes to the system, the other objects give o receive the heat to the other object, until the system stay in thermal equilibrium.
    The first Thermodynamic's law talks about the way that the heat and the work (both, types of transition's energy) mixed to be named intern energy, another variable in Thermodynamics. This law is based in the conservation energy's principle.

    Alejandro Ventura UP170146

  • Nancy Delgado Post author

    Thanks to this video, we can reaffirm a little what was already known about thermodynamics. Here we can also reaffirm that we can learn to create more efficient machines for industrial processes and at the same time be able to take care of our environment and improve technology, because thermodynamics is present on all sides, everything must be in balance to be able to function.
    Nancy Delgado Rodríguez

  • Luz Elena Tiscareño Montoya Post author

    Excellent video to remember the basic concepts of thermodynamics, the relationship between open and closed systems, as well as the considerations that must be made with each of them. For a person who doesn't live with calculations that involve this branch of science, it seems a good tool to start learning. The graphics seemed right to me, especially when he explained the kinetic energy with the Star Wars character. <3

  • alejandra Muñoz Post author

    Thermodynamics show up in our daily lives.
    Engineering is not just about getting more of what we want, but also controlling what we don't want.
    The zeroth law of thermodynamics, what it means to reach a thermal equilibrium, and define the first law of thermodynamics (internal energy + kinetic energy + potential energy = heat added – work done).

    It is important to know the forms of energy, and the types of systems (open and closed). and it is explained in a simple way as the isochoric, adiabatic and stationary processes, as well as understanding the enthalpy, make our daily life easier.
    Alejandra Muñoz
    UP170047/ ENE04A

  • Diego López Cruz Post author

    I can't believe that half of my Thermodynamics course at the university has been summed up in ten minutes! This branch of Physics is truly one of the most important, especially for those who are studying Energy Engineering. And I think the best way to understand all the basics about thermodynamic systems is with simple examples and lots of images. The equations and all the math can be deduced from the understanding of the systems.

    Diego G. López Cruz

  • Nadia Puga Post author

    Wow, in ten minutes i could understand a lot of information about thermodynamics, or explication is very good, the way to put examples about with everyday life, giving with this a greater understanding how a hydroelectric plant works wich helps with the production of energy
    Nadia Brizeida Puga Pérez

  • Tadeo Huerta Post author

    adolfo tadeo huerta garcia, up170690, ene04a, ing. energia. universidad politecnica de aguascalientes. termodyanmics describes how thermal energy is converted to and from other forms of energy. it is one of the main focuses of engineering. because engineer need to know how much heat or work they will get out of an engine if they put energy into it.

  • Nadia Puga Post author

    I know about thermodynamics is that it obviously has to do with energy, heat and work.
    The study of thermodynamic is very important to understand the process of when energy is transformed un to another and with it we can improve the efficiency to lose less energy in the from of heat
    Alejandra Mascorro UP170565

  • Melissa Flores Post author

    Melissa UP170777 in in my opinion this video speaks in a summarized way what is the career that we are studying

  • Jocelyn Valdes Post author

    Thermodynamic has a big branch of obtain energy and is important understand the benefits than get it. The law zeroth of termodynamic is the begin of the rules from the other laws, someone described the pressure, volume and temperature like a equilibrium of the system. I know the 1st law explain about the conservation but I needed to know a little more like energy contained within the system and than the energy can move between boundaries.
    The 1st law has energy kinetic and the potential energy. I think is importan know this topic because I could see and understand more easy.
    Leslie J. Valdés. ENE04A

  • Shyho Gaming Post author


  • Callmeromain2016 Post author


  • Gay Lord Post author

    in one video you stated that energy can neither be created nor destroyed!!! I'M CONFUSED.

  • Grandmaester9 Post author

    Oo antman and wasp reference

  • Savva Pouroullis Post author

    Cengel is such a badass textbook

  • Richard Francis Post author

    The brown girl is so beautiful.

  • Mounir Baroudi Post author

    Anyone have a good textbook recommendation for self-study of these topics?

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