Thermodynamics Definition and 1000 Threads

Homework Statement A concrete driveway is built from identical slabs of concrete, as shown below, which have a length, L, of 3.18 m long at 17.3 C. The concrete slabs have coefficient of linear expansion of 1.20 x 10-5 K-1 and are laid in an area where the temperature ranges from -29.8 C to...

Homework Statement Homework EquationsThe Attempt at a Solution I understand how they got Q1 and Q2 for the first two columns, but how am i suppose to find Q1 and Q1 for the 3rd and 4th event? Isn't it just 0? Cause it seems like the temperatures just stayed constant. I'm not entirely sure...

Homework Statement The initial state of 0.1 mol of an ideal monatomic gas is P0=32 Pa and v0=8m3. The final state is P1=1 Pa and V1=64m3. Suppose that the gas undergoes a process along a straight line joining these two states with an equation P=aV+b, where a =31/56 and b=255/7. Plot this...

Long time no see, PhysicsForums. Nevertheless, I have gotten myself into a statistical mechanics class where the prof is pretty brutal and while I can usually manage, this problem finally has me stumped. I'd like to be nudged in the right direction, not outright given the answer if possible. I...

Homework Statement I don`t know if the image will show so I`m also adding a link to the image of the problem. This problem is a modification my professor made to the one in the link below(*), he changed the rigid diathermic partition into a movable partition. I`m supposed to find the...

MODERATOR'S NOTE: NO TEMPLATE BECAUSE THREAD WAS ORIGINALLY POSTED IN A NON-HOMEWORK FORUM A monoatomic gas is present i n cylinder if its volume increase from 100cm3 to 200cm3 at constant pressure 1*10^5 what is change in internal energy. I tried to solve it but couldn't. I tried to solve it...

Hi all, I am trying to learn more about this field. Whether you work or have worked in this area or not, I would like to know where Soft Matter is going in terms of theory and applications. Thanks, A.D. *I apologize in advance if there are already many threads specifically addressing this...

Homework Statement I really don't know if I'm in the right subforum... I've started reading this text on statistical mechanics from MIT, but I'm stuck on page 2. Here's the statement: Let the equilibrium state of systems A, B, and C be described by the coordinates {A1, A2,· · ·}, {B1, B2,·...

Hello - I am wondering abut the meaning of chemical activity. Most definitions are something along the lines of "effective concentration," which is fine until you have a real concentration in a lab, and you don't know if you need to calculate the concentration or "effective" concentration of the...

Does use of solar panels or other radiation capturing technologies in itself warm the earth? Since solar energy is radiated partially back to space, then, when a portion of it is captured and converted to electricity which performs work and rseleases heat (e.g. in transmission lines) it would...

So, I'm now studying thermodynamics and our teacher proved some time ago the following mathematical result: If f(x,y,z)=0, then (∂x/∂y)z=1/(∂y/∂x)z But today he used this relation for a function of four variables. Does this result still hold, because I'm not really sure how to prove it. If...

I'm working on a project at university to calculate the magnetocaloric effect of dysprosium. This will be done using a new technique designed at the university of which its not necessary to go into detail about. In short, the Dy is placed in a solenoid, through which a current runs, the current...

Has some sense write in the thermodynamics identity the terms TdS and dU at the same side of the equation and with the same sign? what would be this sense?For example PdV=TdS+dU

Greg Bernhardt submitted a new PF Insights post Statistical Mechanics Part II: The Ideal Gas Continue reading the Original PF Insights Post.

Considering the linear thermal dilation formula ΔL=Li*a*ΔT (length change equals initial length times thermal dilation coefficient times temperature change), I was wondering why does it not work backwards? am I using it wrong or is there something missing? For instance if we assume a=5*10^-5 ...

Homework Statement Which of the following statement(s) is (are) correct when an ideal gas goes from an initial to a final state in a single process? a. No work is done on or by the gas when the volume remains constant. b. No energy is transferred into or out of the gas as heat transfer when the...

<Moderator's note: Approved although without template. Member has been warned.> An ideal gas is taken along the path AB (see fig.). If 70 calories of heat is extracted from the gas during the process, calculate the change in internal energy during the process. My attempt : Work done in the...

Hello, I did read one paper about the Carnot cycle in a black hole. https://arxiv.org/pdf/1404.5982.pdf After formula (15) this paper says: 1) "The vanishing of CV is the “isochore equals adiabat” result, specific to static black holes, making our Carnot cycles particularly simple to make...

If the universe keeps expanding and eventually ends in a "big freeze" or heat death, does this contradict the third law of thermodynamics? The third law of thermodynamics states that a crystal at absolute zero has zero entropy. Since the entropy of the universe can never decrease, as the age...

Homework Statement I am preparing a phosphate and a bicarbonate buffer at pH 7.4. I am not using the tradition of making a "rough" buffer and then adjusting the pH to the desired value as I want to target a certain value of osmolarity in both buffers. As such I just want to do all calculations...

Consider the following problem: Gaseous helium (assumed ideal) filled in a horizontal cylindrical vessel is separated from its surroundings by a massless piston. Both piston and cylinder are thermally insulating. The ambient pressure is suddenly tripled without changing the ambient temperature...

Homework Statement I am trying to figure out how to get the V2^2 alone and I feel that this is very basic rearranging of equations but I have been stuck on it forever now. Thank you so much in advance. -75 kj/s= 4.09 kg/s (-190.3 +...

Why can sometimes entropy remain constant with increase of temperature and vice versa?Entropy implies transfer of heat and heat must increase with temperature.I am unable to intuitively understand.

Homework Statement A steam heating system is used in winter season, The radiator of a steam heating system has a volume of 25 liters and is filled with superheated water vapor at 200 kPa and 200C. At this moment both the inlet and the exit valves to the radiator are closed. After a while it is...

Wiki states: Photon upconversion (UC) is a process in which the sequential absorption of two or more photons leads to the emission of light at shorter wavelength than the excitation wavelength. https://en.wikipedia.org/wiki/Photon_upconversion Is it possible to have the emitted light with the...

Why is entropy lost by hot water less than the entropy gained by the cold water?From perspective of energy,why is it better to take water and heat it to a temperature than it is to mix hot water and cold water to get a particular temperature.

Hello, being kind of new to thermodynamics, does anybody have any recommendations where a good place to start learning is. Any online info or textbook I could buy? Thanks

Homework Statement N2 + 3H2 --> 2NH3 (all gases) Why is such a high pressure needed? Calculate the equilibrium constant at 500k then estimate the percentage conversion at equilibrium at 1 bar total pressure, assuming the stoichiometric ratio of N2:H2 is 1:3. Repeat the process at 50 bar...

So it is stated that exothermic reactions are the ones where the heat of reaction is positive and endothermic reactions are the ones where the heat of reaction is negative. My question is: why is this so, when in the 1st law of thermodynamics, where ΔU=Q+W it is stated that Q is positive if...

Homework Statement Unit mass of a fluid at a pressure of 3 bar, and with a specific volume of 0.18 m^3/kg, contained in a cylinder fitted with a piston expands reversibly to a pressure of 0.6 bar according to the law p = c/v^2 , where c is a constant. Calculate the work done during the...

Homework Statement A sample of K (s) of mass 2.740g undergoes combustion in a constant volume calorimeter at 298.15K . The calorimeter constant is 1849 J/K , and the measured temperature rise in the inner water bath containing 1450 of water is 1.60K Calculate the internal energy of formation...

Homework Statement [/B] In a closed system a gas is compressed from a pressure of 3 bar absolute to a pressure of 5 bar absolute, and its volume changes from 0.9m^3 to 0.6m^3 according to the law P1V1^n = P2V2^n. Calculate: The value of the index n. Homework Equations P1V1^n = P2V2^n The...

Homework Statement A 3-ft^3 container is filled with 2-lbm of oxygen at a pressure of 80 psia. What is the temperature of the oxygen?Homework Equations pV= nRT T= PV/nR R= 10.7316 psia x ft^3/ lbmol x R The Attempt at a Solution Hi everyone! So I understand how to use the Ideal Gas Law but my...

Recently read this article on Physorg: https://phys.org/news/2018-01-efficiency.html My questions are: 1. If "converting" information into energy requires a system (the demon I suppose) having a photodiode, processor, laser (light trap) all expending energy in order to cause the conversion...

Homework Statement What is constitutional undercooling? What are it's effects? Homework EquationsThe Attempt at a Solution Undercooling is when the liquid has a below freezing temperature. However konstituntial undercooling occurs during solidification when the liquid is brought to freezing...

Homework Statement I am working on a problem where I need to determine the time taken for an air heater with an 8kW output to heat a volume of air of 9m^3 by 25C. I am neglecting all losses at the moment. It almost seems too simple in my mind that I'm concerned I'm overlooking...

Greg Bernhardt submitted a new PF Insights post Statistical Mechanics Part I: Equilibrium Systems Continue reading the Original PF Insights Post.

Homework Statement You add 1500 cal of heat to a cup of water at 22.5ºC. The water has a mass of 500.0g. What is the final temperature of the water? Homework Equations Q=mcΔT The Attempt at a Solution so i tried solving it by finding the energy of the water Q=(500g)(1.0cal/g)(22.5ºC) Q=11250...

Homework Statement The issue is the word 'increase' in c)iii), where I'm pretty sure the wording should have been 'decrease' or at least 'change', since both the work done and the heat removed have a negative value. Homework Equations dU = dQ + dW (1st law) The Attempt at a Solution My...

Homework Statement Homework EquationsThe Attempt at a SolutionTaking the engine to be a Carnot engine, ## \eta = \frac { T_h – T_c } {T_h} = \frac { W} {Q_h} ## ...(1) ## Q_h = C(T_h – T_f) ...(2) \\ Q_c = C(T_f – T_c) ...(3) \\ W = Q_h – Q_c = C(T_h + T_c – 2 T_f) ## ...(4)Solving...

Homework Statement A hydrocooling unit can cool fruits and vegetables from 30 to 5 C at a rate of 20,000 kg/h under the following conditions: the channel is 3 m wide by 90 cm high. The water is circulated and cooled by the evaporator section of a refrigeration system. The refrigerant...

Advanced Problems textbook. (It's on pages 212-213). I'll post the question and following it the solution in the book: The question: The Solution: What I don't understand is how did they arrive at the identities with ##\frac{\bar{G}_1''-\bar{G}_1'}{0}## and...

Homework Statement Homework EquationsThe Attempt at a Solution ## \frac 1 2 m<v_x^2> =\frac 1 2 k_BT , \\ \sqrt{ <v_x^2>} = 556~ m/s ## So, I guess that the standard deviation should be less than rms speed. So, the option is (a) ## \left< ax + b \right> = a\left<x\right> + b...

I am struggling to fully grasp the concept of flow work for a non-deformabable control volume. Nearly every source puts it in this way: flow work is the work required to push fluid into and out of the control volume and as such is defined as Pv on a unit mass basis. But how can this work be...

Hi all. Suppose I have the ideal gas law $$P=\frac{RT}{v}$$If I'm asked about the partial derivative of P with respect to molar energy ##u##, I may think "derivative of P keeping other quantities (whatever those are) constant", so from the formula above I get $$\frac{\partial P}{\partial...

I was thinking about the expansion of space. It seems clear that objects that are bound by gravitation or the strong nuclear force do not experience an increase in size as the universe continues it's expansion. However, such systems do contain abundant space. It is argued that gravitation and...

Homework Statement Homework Equations F= ma P= F/A The Attempt at a Solution a). Assuming the piston is in equilibrium, I'm applying Newton's second law F=ma=0 Equals zero because it is not moving Note: P=F/A which I rearrange to solve for the force for F= PA. This represents the...

Homework Statement Homework EquationsThe Attempt at a Solution I think the correct option is (a) and (d) from the book reading.About the option (c), the second law of thermodynamics tells us the direction of heat flow. I think it is a fundamental law, it could not be derived.

Homework Statement A thin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. The rod (A) has a thermal conductivity of kA = 0.15 W/(m*K), while the tube (B) has a thermal conductivity of kB = 1.5 W/(m*K) and its outer...

I have a doubt regarding the answer, a box separated by a movable wall has two compartments filled by a monotonic gas .Initially the volumes are equal but the pressure are 3P and P respectively .When the wall is allowed to move the final pressure is...