What is Kinetic theory: Definition and 144 Discussions

The kinetic theory of gases is a simple, historically significant classical model of the thermodynamic behavior of gases, with which many principal concepts of thermodynamics were established. The model describes a gas as a large number of identical submicroscopic particles (atoms or molecules), all of which are in constant, rapid, random motion. Their size is assumed to be much smaller than the average distance between the particles. The particles undergo random elastic collisions between themselves and with the enclosing walls of the container. The basic version of the model describes the ideal gas, and considers no other interactions between the particles.
The kinetic theory of gases explains the macroscopic properties of gases, such as volume, pressure, and temperature, as well as transport properties such as viscosity, thermal conductivity and mass diffusivity. The model also accounts for related phenomena, such as Brownian motion.

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  1. J

    Quantum Kinetic Theory by M. Bonitz: Traces over Commutators

    Hi! Has anyone studied the book Quantum Kinetic Theory by M. Bonitz? I am reading it on my own and have a hard time understanding some of the things that are done in the book. Specifically, in the second chapter, he keeps terms which are traces over a commutator. Isn't the trace over a...
  2. S

    Superman and the Kinetic Theory of Gases

    Homework Statement Superman leaps in front of Lois Lane to save her from a volley of bullets. In a 1-minute interval, and automatic weapon fires 150 bullets, each of mass 8.0g, at 400 m/s. The bullets strike his mighty chest, which has an area of 0.75 m2. Find the average force exerted on...
  3. T

    Velocity vs Momentum: Kinetic Theory & Relativistic Systems

    Why is it in kinetic theory one uses the velocity variable, instead of the momentum variable? Wouldn't this cause problems when trying to generalize to relativistic systems?
  4. R

    Exploring the Significance of 1/4 in Kinetic Theory's Molecular Flux Formula

    The molecular flux (number of collisions per unit area per unit time) in Kinetic theory is given by F=\frac{1}{4} n \bar{c} where c bar is the average molecular speed and n is the density of molcules in the gas phase (molecules/m^3) I was wondering about the origin of the 1/4 term ...
  5. R

    Kinetic Theory of Gas question involving viscosity

    Homework Statement PLEASE help! I really should be able to do this but am so stuck: Two plane disks, each of radius 5 cm, are mounted coaxially with their adjacent surfaces 1 mm apart. They are in a chamber containing Ar gas at S.T.P. (viscosity 2.1×10−5 Nsm−2) and are free to rotate...
  6. T

    Kinetic Theory - Free Path Distribution

    Homework Statement I'm slightly confused as to how to work out the distribution of free paths (the distance a particle travels before colliding). Finding the mean free path is fine, but there are several questions that I'm currently attempting that would seem to need the distribution of path...
  7. E

    Kinetic Theory of Gases & Escape Speed

    Homework Statement In the first 2 parts of the problem, I calculated at what temperatures the rms speeds vrms of H2 molecules and O2 molecules would equal the escape speed of Earth (11200 m/s). The answers I calculated for this were 10000 K for H2 and 160000 K for O2. Those answers are...
  8. L

    Kinetic theory of gases momentum

    p=momentum=(mass*volume) delta px = pf - pi mvf - mvi mvx - (-mvx) <<<<---- where does this second negative come from ? what am i missing here? 2mvx in my book it shows that delta px = - mvx - (mvx) = -2mvx
  9. I

    Kinetic theory and temperature in gases

    Homework Statement Temperature of a gas (in kelvin) is proportional to the average kinetic temperature of its particles. Question: The temperature of 55k (277C) to 1100k(827C). At 277C the mean kinetic energy of the gas is 1.14x10^20. What is it at 827C?Homework Equations kinetic energy= ½ x...
  10. B

    How Can Kinetic Theory Explain Differences in Latent Heat and Uniform Diffusion?

    Homework Statement 1)It is observed that the latent heat of vaporization is greater than the specific latent heat of fusion for most substances. Use kinetic theory to explain this in terms of the particles in each state. 2)When a drop of potassium dichromate is added to a beaker of water...
  11. B

    Kinetic theory of gasses Integration problem

    Homework Statement In the temperature range 310 K and 330 K, the pressure p of a certain nonideal gas is related to volume V and temperature T by p = (24.9 J/K) T/V - (0.00662 J/K2)T^2/V How much work is done by the gas if its temperature is raised from 314 K to 324 K while the pressure is...
  12. M

    Help Needed in Pressure and Kinetic theory of GAses

    Homework Statement A thin tube of uniform cross-sectionis sealed at both ends . when it lies horizontally,the middle 5cm length contains mercury and the 2 equal ends contain air at the same pressure P. When the tube is held at an angle 60\circ , then the lengths of the air columns above and...
  13. R

    Kinetic theory in general relativity

    need some help clarifying kinetic theory (what it means, equations associated with it and what it pertains to, limits etc...) thanks, rubecuber
  14. I

    Kinetic Theory Of Gases - radiometer

    This is a question relating to a Crooke's radiometer: Assume that due to absorption, the local temperature close to the black surface is T = 50C, while the temperature close to the white surface is T = 20C. For a gas with density n = 2:5 x 10E20m-3, compute the net force on one blade of area...
  15. P

    Kinetic theory for the molecular condensation flux

    Homework Statement Start with the kinetic theory formula for the molecular condensation flux, \Phi_cond = 1/4 n_v*c_v, where n_v is the number density of vapor molecules just above a liquid water surface and c_v is the mean speed of the vapor molecules. Derive an expression for calculating...
  16. S

    Questions about kinetic theory

    May you professors please check part b of my work because my answer does not match the answer in the back of the book. Thank you. Question: (a) What is the total random kinetic energy of all the molecules in 1 mol of hydrogen at a temperature of 300 K? (b) With what speed would a mole of...
  17. P

    Derivation for Kinetic Theory of Gases

    My question is with regard to the derivation for the kinetic theory of gases that allows us to relate temperature to the motion of the particles. I've looked at several introductory Physics texts and the same derivation is given (derivation in italics, my question in red, regular font): To...
  18. L

    Calculating Molecule Speed Ratios in a Gas Mixture

    Homework Statement 1) A container is filled with a mixture of nitrogen and oxygen. What is the ratio of the rms speed of oxygen molecules to that of a notrigen molecules? (molar mass of oxygen = 32 g/mol; molar mass of nitrogen = 28 g/mol) 2) By what factor does the rms speed of neon...
  19. C

    Kinetic Theory of Gases and speed of oxygen molecules

    Homework Statement A syringe of volume 20 ml has just been used and now lies empty on the doctor's desk. The pressure in the office is 100,000 Pa. Assume that the air is an ideal gas consisting of nitrogen N2 (80%) and oxygen O2 (20%) molecules. k=1.38×10-23 J/K and the molar mass of oxygen is...
  20. V

    What is the Work Done by an Ideal Gas Expanding at Constant Temperature?

    Homework Statement Two moles of an ideal gas expand to double the initial volume at a constant temperature of 400 K. Calculate the work done by the process. Homework Equations W=2.303nRTlog(v2/v1) The Attempt at a Solution i tried the formula and got 4613.959 J but the answer is 554.6 J
  21. G

    Understanding of Kinetic theory of matter

    Is this correct? - The density of substances decreases for the transition between solidà liquid, and liquid--> Gas (exception to this rule is for water, where the soli--> liquid transition causes the substance to contract instead of expand, hence increasing density) [at higher pressures...
  22. P

    Apply kinetic theory to solids and liquids?

    My chemistry textbook tries to explain the properties of solids and liquids with the kinetic theory. Is this not good? Should only gases be explained by the kinetic theory since one of the postulates in this theory is that particles exert no forces on each other. The book had to disable this...
  23. A

    What is the Force Exerted by a Gas on a Container Wall?

    The problem I'm working on is verbatim as follows: "A sealed cubical container 20.0 cm on a side contains three times Avogadro's number of molecules at a temperature of 20.0 degrees Celsius. Find the force exerted by the gas on one of the walls of the container." So, I would assume that I need...
  24. G

    Why can't helium reach 0 K and become solid according to kinetic theory of gas?

    Can we explain the rising of smoke on the basis of kinetic theory of gas ?
  25. G

    Gas Expansion and Work: Effects on Internal Energy and Temperature

    A cylinder containing a gas is lifted from the first floor to the second floor .What is the amount of work done on the gas ? What is the amount of work done by the gas ? Is the internal energy of the gas increased ? Is the temperature of the gas increased ? consider 2 cases : case 1 : the...
  26. F

    Why do hydrogen molecules travel at 4000mph in the Kinetic Theory of Gases?

    Apologies if it's been asked before, but this came up on another thread. The Kinetic Theory of Gases says that hydrogen molecules at room temperature and pressure are traveling at circa 4000mph. So if I were to suddenly decap a canister of hydrogen in a vacuum chamber, I should see molecules...
  27. Amith2006

    AZING RESULTS: Why is the gaseous state the state of greatest potential energy?

    Sir, Why is the gaseous state called the state of greatest potential energy?
  28. Amith2006

    Kinetic theory of gases and volume

    Sir, Please help me with this problem. # A fixed mass of gas at constant pressure occupies a volume V. The gas undergoes a rise in temperature so that the root mean squared velocity(c) of the molecule is doubled. What is the new volume? I solved it in the following way:- Let V1 be the...
  29. Amith2006

    What is the relationship between intermolecular distance and pressure?

    4)Sir, Please give a hint to solve the following problem. # In order to double the separation between the molecules (keeping the temperature fixed), how many times the initial pressure should the final pressure be made? How do you relate intermolecular distance and pressure?
  30. Amith2006

    Kinetic Theory of Gases homework

    3)Sir, Please help me with this problem. # If one mole of a mono atomic gas(r = 5/3) is mixed with one mole of a diatomic gas(r = 7/3),then what is the value of the r for the mixture? In the above problem r = C(p)/C(v) = ratio of specific heats.
  31. Amith2006

    Does the magnitude of C in Boyle's Law depend on the quantity of gas enclosed?

    1) According to Boyle’s law, PV = C (At constant temperature) Where C is the constant of proportionality. Is it true that the magnitude of C depends upon the quantity of gas enclosed?
  32. Q

    Kinetic theory of gases - can someone check this please?

    i'm given that p= \frac{1}{3}\rho\overline{c^2} without calculation, what happens to rms speed if pressure halved, temperature constant? firstly, just from rearranging the original equation, you get \overline{c^2} = \frac{3p}{\rho} square rooting both sides to get rms speed gives...
  33. K

    How Does Molecular Kinetic Theory Explain the Behavior of Helium Gas Molecules?

    :confused: :redface: Hi got this question with which i need help For 1.0 mol of helium at a temprature 27deg C calculate:- i) the total kinetic energy of molecules, ii) the root mean square speed of the molecules
  34. A

    Work, Energy, Fluids, Temperature, and Kinetic Theory

    Okay, I need help on a lot questions. I most of the math parts, but this stuff just completely confuses me. Any help will be greatly appreciated. Please help me not fail my class. Work/Energy Two identical arrows, one with twice the speed of the other, are fired into a bale of hay. Assuming...
  35. S

    How Does the Kinetic Theory of Gases Explain Gas Movement in a Cylinder?

    Kinetic Theory of Gases... Little help please :) Hey, i didnt seem to have trouble with any other questions except this one... all i could figure out is that i somehow must use the kinetic theory of gases? A massless cylinder 34 cm long rests on a horizontal frictionless table. The cylinder is...
  36. A

    Kinetic theory of gases in cylinder

    Two gas cylinders are identical. One contains the monatomic gas argon (Ar), and the other contains an equal mass of the monatomic gas radon (Rn). The pressures in the cylinders are the same, but the temperatures are different. Determine the ratio KEAvg,radon / KEAvg,argon of the average kinetic...
  37. K

    The Consequences of Inelastic Collisions in Kinetic Theory

    In the kinetic theory, it is supposed that the molecules make elastic collisions with the walls of the container. Imagine that the collisions were inelastic. Describe and explain the consequence of this with regard to the temperature of the gas. So far, i have said that not all of the molecules...
  38. I

    Kinetic Theory Of Temperature Problem

    The rms speed of the molecules in a gas is 600ms^-1 and the mass of the molecules is 4.6*10^-26kg. What is the temperature of the gas in degrees Celcius? v_{r.m.s.}\=\600\ms^-1 \\ m\=\4.6x10^-26kg \\ n\=\6.022x10^23 \\ r\=8.31\j\k\mol^-1 \\ \\ \\ rt\=\frac{\2}{3}\(\frac{\1}{2}m<v^2>)\\...
  39. Clausius2

    Kinetic Theory and Thermophysical Properties

    Is there any way to derive the viscosity \mu of an ideal gas from kinetic theory? Also: Is there any way to derive the mass diffusitivity D of an ideal gas from kinetic theory?. Another one: does it make sense to talk about the mass diffusivity of an individual gas (for instance D_i), or...
  40. U

    Kinetic Theory of Gases Problem

    ok, I am having trouble understanding exactly what this problem wants from me, its asking: At what temperature would the translational rms speed of hydrogen molecules be equal to that of oxygen molecules at 300K? and the answer it gives me is 19K... but I really have no idea where to even...
  41. A

    How Does Energy Transfer Affect Temperature and Work in Gas Processes?

    A 1.00 mol sample of an ideal monatomic gas is at an initial temperature of 300 K. The gas undergoes an isovolumetric process acquiring 500 J of energy by heat. It then undergoes an isobaric process losing this same amount of energy by heat. Determine a) the new temperature of the gas and b)...
  42. P

    Temperature and Kinetic Theory

    An aluminum bar has the precisely desired length when at 15°C. How much stress is required to keep it at this length if the temperature increases to 35°C? How do I do this? can anyone help me please...
  43. exequor

    How does temperature affect the speed of gas molecules?

    by what factor does i. the mean square speed ii. the root mean square speed ... of molecules of a gas increase when its temperature is doubled. I can tell that it would be 2 and 2^0.5 for the answer but is there a way to use the expressions to find that?
  44. T

    Pf = 157.47 Kinetic Theory Homework Help: Raindrop Collisions and Ideal Gas Laws

    Kinetic theory HW help :( I am new here and found the site while trying to find a formula. I am having problems solving some questions. I worked out what i could but don't know if i did it right. Please Help :( PROBLEM 1 A raindrop of mass (1mg) fall vertically at a constant speed of...
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