The gas laws
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The Gas Laws. Kinetic Molecular Theory. Postulates of the Kinetic Molecular Theory of Gases. Gases consist of tiny particles (atoms or molecules) These particles are so small, compared with the distances between them, that the volume (size) of the individual particles can be assumed

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The Gas Laws

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The gas laws

The Gas Laws


Kinetic molecular theory

Kinetic Molecular Theory

Postulates of the Kinetic Molecular Theory of Gases

  • Gases consist of tiny particles (atoms or molecules)

  • These particles are so small, compared with the distances between

    them, that the volume (size) of the individual particles can be assumed

    to be negligible (zero).

    3. The particles are in constant random motion, colliding with the walls of

    the container. These collisions with the walls cause the pressure exerted

    by the gas.

    4. The particles are assumed not to attract or to repel each other.

    5. The average kinetic energy of the gas particles is directly proportional

    to the Kelvin temperature of the gas


Kinetic molecular theory kmt

Kinetic Molecular Theory (KMT)

AS TEMP. , KE

  • explains why gases behave as they do

  • deals w/“ideal” gas particles…

1.…are so small that they are assumed to have zero volume

  • …are in constant, straight-line motion

  • …experience elastic collisionsin which no energy is lost

  • …have no attractive or repulsiveforces toward each other

  • …have an average kinetic energy (KE)that is proportional

    to theabsolute temp. of gas (i.e., Kelvin temp.)


Model gas behavior

Model Gas Behavior

All collisions must be elastic

Take one step per beat of the metronome

Container

Class stands outside tape box

Higher temperature

Faster beats of metronome

Decreased volume

Divide box in half

More Moles

More students are inside box

Mark area of container with tape on ground.

Add only a few molecules of inert gas

Increase temperature

Decrease volume

Add more gas

Effect of diffusion

Effect of effusion (opening size)


Kinetic molecular theory1

Kinetic Molecular Theory

  • Particles in an ideal gas…

    • have no volume.

    • have elastic collisions.

    • are in constant, random, straight-line motion.

    • don’t attract or repel each other.

    • have an avg. KE directly related to Kelvin temperature.

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem


Real gases

Real Gases

  • Particles in a REAL gas…

    • have their own volume

    • attract each other

  • Gas behavior is most ideal…

    • at low pressures

    • at high temperatures

    • in nonpolar atoms/molecules

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem


Properties of gases

Properties of Gases

Gas properties can be modeled using math.

Model depends on:

V = volume of the gas (liters, L)

T = temperature (Kelvin, K)

P = pressure (atmospheres, atm)

n = amount (moles, mol)

PV = nRT

The ideal Gas Law


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