Gases Definition and 501 Threads

Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide). A gas mixture, such as air, contains a variety of pure gases. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible, as indicated by the constant velocity vectors in the image.
The gaseous state of matter occurs between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention.
High-density atomic gases super-cooled to very low temperatures are classified by their statistical behavior as either Bose gases or Fermi gases. For a comprehensive listing of these exotic states of matter see list of states of matter.

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  1. 5

    Hot gases flow better than cold gases why?

    I have read that hot gases flow better than cold gases. Why is this so? Less dense? Any good readings on it. I am thinking of incoming intake charge (cool) in an engine, and the outgoing (hot) gases. Thanks.
  2. I

    Hartree-Fock wave function for a mixture of two oppositely charged gases

    Hi, Suppose there is half-half a mixture of an electron gas and a gas of some hypothetical particle with the same mass, spin but an opposite charge (like positrons that don't decay). Would anyone be able to tell me how the Slater determinants combine in this case? The HF wave function for just...
  3. L

    About a mixture of gases and the equilibrium distribution

    Hello: I've been reading about the Maxwell Boltzmann distribution for a dilute gas. One of the hypotheses to get this result is that there is only a chemical species within the box, but what would happen if you put a mixture of gases, say two or three, each of which is very dilute and you...
  4. W

    Nitrogen Gas Molecule Speeds and Temperature Relationship

    Homework Statement Fractions of Molecules in an Ideal Gas with Speeds Less than Various Multiples of v/v_{\rm rms} in the textbook. The molar mass of {\rm{N}}_2 is 28.0 {\rm{ g/mol}}. For a gas of nitrogen molecules {{\rm{N}}_2 } , what must the temperature be if 94.7\% of all the...
  5. J

    Exploring the Stable State of Noble Gases

    Hi, I am a student currently engaged in AP Physics B and AP Physics C, and I am curious as to why it is that most of the Noble Gases exhibit and exist in such a stable state. In AP Chem last year I learned that having a configuration in which the valence shell of an atom has eight electrons...
  6. J

    Proving Internal Pressure of Ideal & VdW Gases

    Like in the other problem I posted- This is the other question that I missed and just can't find a solution for. Homework Statement Prove the internal pressure is 0 for an ideal gas and ((n^2)a)/(v^2) for a Van der Waals gas. Homework Equations 1. VdQ Eqn: p= (nRT)/(v-b) -...
  7. H

    How Does Temperature and Depth Affect the Volume of an Air Bubble in Water?

    [SOLVED] Ideal gases an air bubble of volume 20cm^3 is at the bottom of a lake 40m deep where the temp is 4C, the bubble rises to the surface which is at temp 20C, take the temp of the buble to match that of the surrounding water, just as the bubble reaches the surface, what is it's volume...
  8. M

    Discovering Gas Compressibility: 8th Grade Science Fair Project

    Hello everyone. We are working on a 8th grade science fair project. We are trrying to conduct experiments that will let us find the relationship of a particular gas's compressabilty and its temerature increase when compressed. We are trying to make the project reletivly advanced, and hope to be...
  9. T

    Theoretical treatment to determine speed of sound in gases

    Homework Statement Using a theoretical treatment including \gamma (the ratio of cp to cv), determine the speed of sound in each of these gases: argon at 273 K, methane at 165 K, nitrogen at 600 K. Answer must be applicable to any gas at any temperature Homework Equations The...
  10. S

    Exploring Kinetic Models of Liquids and Gases

    sorry to ask this stupid question... can anyone tell me exactly the difference between liquid and gas based on kinetic model? most textbooks give that in liquids inter molecular spaces are lesser than gases ,etc & etc but if compress the gas to much ,still it doesn't get converted into...
  11. 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...
  12. F

    Adiabatic & Quasistatic Expansion of Photon & Fermion Gases

    Homework Statement 1.Show that PV^Y is a constant for adiabatic,quassistatic expansion of a photongas and determine Y 2. Show the same for full degenerate gas of fermions at T=0 Homework Equations The Attempt at a Solution Plz help thx
  13. A

    Which of the following is NOT true about gases?

    Which of the following is NOT true about gases? 1. The volume a gas occupies is directly proportional to its molecular weight. 2. The gas is at STP if it is at 273 K and 1 atm. 3. Gases exert pressure on their surround- ings. 4. Gases can expand without limit. 5. The density of a gas...
  14. O

    Determine the fraction of the volume

    [SOLVED] Ideal Gases Homework Statement A gas has a temperature of 310K and a pressure of 101kPa (a.) find the volume occupied by 1.25 mol of this gas, assuming its ideal. (b.) assuming the gas molecules can be approximated as a small sphere of diameter 2.5x10^-10, determine the fraction of...
  15. S

    Calculating vrms of Helium in Mixture of Gases

    Homework Statement A gas bottle contains a mixture of Helium and Oxygen molecules (O2 is diatomic). The root-mean-square velocity for the O2 molecules is 482 m/s. Find vrms for the Helium atoms. Homework Equations 1/2mv^2=1/2mv^2 and solve for velocity of He, however, i am not...
  16. B

    What Could Cause Large Percent Deviation in Graham's Law Experiment?

    Homework Statement This is for an experiment. I determined the theoretical diffusion ratio of ammonia to hydrogen chloride to be 1.46:1 but my experimental error to be 4.20:1. This means that my percent deviation was around 200%. Question is, what are the reasons for the large percentage...
  17. 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...
  18. G

    Thermodynamics and Relativity: observing gases, rel. effects

    Few weeks ago a respected magazine brought some excitement with a story on missing bond between Thermodynamics and Relativity. My question is what satisfies the definition of relativistic gas and how would that differ from single star systems with shifted spectra? Take for example...
  19. S

    Why Does H2O Not Appear in Bulb C?

    [SOLVED] Gases Problem Hi Everyone, I was wondering if someone can explain the following question: An apparatus consists of three temperature-jacketed 1.000 L bulbs connected by stopcocks. Bulb A contains a mixture of H2O (g), CO2 (g), and N2 (g) at 25'C and a total pressure of 564 mm Hg...
  20. A

    Ideal gases: irreversible transformation

    A balloon featured with a negligible thermal capacity contains V_{l}=3l of ideal gas and is immersed in a lake (thermal bath) at the depth of h_{l}=10m beneath the lake surface. If it is brought to the depth of h_{l}=3m, how much is the heat exchange?
  21. 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...
  22. S

    Ideal Gases: What Kind of Work?

    Ideal Gases and "Work" Hi When I read up on ideal gases I always find people talking about work extracted from ideal gases. But what kind of work are they talking about? Cheers.
  23. S

    Do Ideal Gases Absorb Heat When Expanded?

    Hi, Do IDEAL gases absorb heat when they expand? I asked a few people this question, half said yes and half said no. Im after a simple yes or no answer with a small explanation to clarify this one. If anyone knows, please reply. Cheers! :smile:
  24. F

    Quicklime: Properties & Uses for Drying Gases

    Quicklime is used to dry gases.It is also basic in nature. It cannot be used to dry acidic gases such as sulphur dioxide and carbon dioxide. Why is this so? Is it because alkali (quicklime) will react with the acidic gases to form salt and water? Please help. Thanks. :smile:
  25. 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...
  26. D

    Leak rate correlation between different gases

    Hi I am i new member, i hope i am posting in the correct forum. I require some help i with a problem i am trying to solve in my work. Currently we have 3 separate leak test methods specified for a part all with different working gases and pressures. If possible, i would like to correlate this...
  27. 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...
  28. M

    Comparing Volumes of Gases in 2 Cylinder Containers

    I want to ask if I have 2 cylinder container 1) 50 m3 2) 60 m3 If I inject the same no. of mole of gases into these containers respectively when I apply PV=nRT Is the volume in calculating the gases in these containers are the same??
  29. 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
  30. P

    Why Does My Ideal Gas Formula Derivation Not Include Moles?

    I'm trying to show a formula for an ideal gas, but I don't get the right results. Homework Statement For an ideal gas PV = nRT where n is the number of momles. Show that the heat transferred in an infinitesimal quasistatic process of an ideal gas can be written as dQ = \frac{C_V}{nR}VdP...
  31. Loren Booda

    Can Noble Gases Be Combined for More Vibrant Colors?

    The noble gases when electrically stimulated emit different visible wavelengths. Can they be combined for a greater variety of coloration?
  32. E

    What is the significance of high-speed gas particles in Earth's atmosphere?

    The Earth's atmosphere is lacking in gases like hydrogen and helium because at a given temperature, a 'significant fraction' of hydrogen or helium particles have speeds greater than Earth's escape speed, while gases like oxygen only have a 'negligible fraction' of the total number of particles...
  33. K

    How Do Initial Pressures Compare in Two Heated Monatomic Gas Containers?

    Homework Statement Two 800 cm^3 containers hold identical amounts of a monatomic gas at 20 C. Container A is rigid. Container B has a 100 cm^2 piston with a mass of 10 kg that can slide up and down vertically without friction. Both containers are placed on identical heaters and heated for...
  34. M

    Temperature Dependence on Pressure Change in Gases

    I have a simple question. If we increase the pressure of a gas by decreasing its volume without heat exchange, does the temperature always change? Or does it depend how fast we change the pressure? I tried to find the answer for this question, unfortunately I couldn’t. Thanks for any help!
  35. P

    Gases & Pressure: Solving Homework Equations

    Homework Statement An expandable cylinder has its top connected to a spring with force constant 2.00 103 N/m. (See Fig. P10.58.) The cylinder is filled with 4.00 L of gas with the spring relaxed at a pressure of 1.00 atm and a temperature of 20.0°C. (a) If the lid has a...
  36. 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...
  37. T

    Calculating Gas Consumption for Scuba Diving: A Homework Problem Solution

    Hi, I have been struggling a little with this question. Scuba divers breathe a mixture of O2(g) and He(g) to avoid "the bends, a condition caused by nitrogen in the blood. If 65.0g O2(g) and 2.00g He(g) are placed in a 5.0L tank at 25oC, calculate: If the average human takes 15 breaths...
  38. A

    Discover the Distance 2 Gases Meet | Urgent Help Needed!

    Urgent Help Needed! (gases) I need some urgent help with figuring out how to find the distance which 2 gases will meet in this question.. Given: Samples of HBr gas and NH_3 gas are placed at opposite ends of a 1.80 m tube. Question: If the two gases are allowed to diffuse through the tube...
  39. A

    (ceramics) random walk approach to gases, liquids, or solids

    For the random walk approach to gases, liquids, or solids, why isn't there a gradient? The atoms don't jump by themselves, right? They should have to feel forces to jump...
  40. Clausius2

    Ideal Gas: Equation Of State in Diatomic Gases: still valid?

    That came out in my qualifying exam. The question was if a gas with rotational and vibrational energies enhanced, does obey the Ideal Gas Equation PV=NKT. You can answer with all the tools you have at hand. My comitee member didn't agree with me, but anyway I persisted in my answer and I...
  41. 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...
  42. B

    Hcl charcteristics - gases recovery

    Hello, I work on a project on the recovery of gases HCl 33 % which escape during the load of this last one in tanks. I want to know if you can help me or propose me a solution for the calculation of this quantity and if you have an idea of a method to get back them. or any information about the...
  43. B

    Recovering Gases HCl 33%: Solutions & Calculations

    Hello, I work on a project on the recovery of gases HCl 33 % which escape during the load of this last one in tanks. I want to know if you can help me or propose me a solution for the calculation of this quantity of gas and if you have an idea of a method to get back them. or any information...
  44. 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...
  45. V

    Gases Homework Help - Calculating Moles & Explaining Water Vapour Pressure

    heres a question-(tough one)..i jus wunna check my answer.. a small sample of magnesium was placed into a reaction flask as shown. HCL acid was added and the hydrogen gas generated wus bubbled through water into a gas collection tube.when the reaction reached completion, the gas collection...
  46. M

    Understanding Gas Compressibility: Exploring Different Approaches and Units

    Is there a unit to measure the compressability of a gas? What gases are the hardest to compress? The easiest? Any links to a better understanding?
  47. B

    Adiabatic Processes and Ideal Gases

    Hey. Im doing this question where Air (said to be ideal gas) is compressed from a pressure of 0.1 MPa and Temp 300K to pressure .5 MPa and temperature 480K. We are supposed to determine whether the process is possible to do adiabatically (sorry if that is the wrong spelling). I hadnt done...
  48. Amith2006

    Average kinetic energy of all gases are the same

    Sir, Is it true that the average kinetic energy of all gases are the same at the same temperature? For example at the same temperature the molecules of hydrogen, oxygen,etc. have the same energy irrespective of their different atomic weights.
  49. A

    Boltzmann distribution and ideal gases

    We know the Maxwell-Boltzmann distribution for the energy and the speed of a molecule of an ideal gas. Using derivatives it is easy to see that the most probable speed for a gas molecule is given by sqrt(2kT/m), which corresponds to kinetic energy kT. Calculating the most probable energy, we get...
  50. S

    The repulsion of the atoms of gases

    Is it possible to imitate the repulsion of atoms of gas on macro-scale? (I mean: atoms of gases repell all other atoms around it using some force. Among them there is nothing (vacuum) - isn't it. Well... - imagine if you could make a macro-object that could repell all matter (atoms) (a sort...
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