Kinetic Molecular Theoryof Gases
Grade 11ES Chemistry
States of Matter: Solids, Liquids, Gases
But how do particles behave?
Kinetic Molecular Theory of Gases1860:Maxwell and Boltzmann were
chemists who first came up with the kinetic molecular theory of
gases. The KMT describes: -Particle size -Particle motion -Particle
energy
Kinetic Molecular Theory of Gases[1] Particle Size of gases: -
Particles are small, separated by empty space. - Their volume is
small compared to the volume of the empty space. - No significant
forces of attraction or repulsion since they are far away from each
other.
Kinetic Molecular Theory of Gases[2] Particle Motion in gases: -
Particles are in constant random motion. - Move in straight line,
unless they collide with something. - Collisions are elastic.(Total
kinetic energy doesn t change).
Kinetic Molecular Theory of Gases[3] Particle Energy in gases:
Kinetic energy,
KE = mv2
All particles have different velocities, so the kinetic energy
of every particle is different. The average kinetic energy of the
gas is determined by measuring Temperature.
Use the KMT of Gases to explain the following: Gases have low
density. Gases can be compressed and they can expand. Gases can
diffuse and effuse.
Gases have low density! According to the KMT, gases occupy large
volume compared to their small mass. Density = mass/volume.
Gases Compression & Expansion!Compression: According to the
KMT, gas particles have large amount of empty space between them.
Expansion: According to the KMT, gas particles are in constant,
random motion.
Gas Diffusion & Effusion!Diffusion: is the movement of one
material into other. Ex: smell of cooking or perfume. Effusion:
when the gas escapes through a tiny opening. Ex: when a tire or
balloon is punctured.
Why do gases diffuse? And effuse?According to the KMT, gas
particles have no significant forces of attraction or repulsion, so
the particles would easily diffuse and effuse.
Graham s Law of Effusion:
Lighter particles diffuse faster than heavier particles.
Using thatWe can compare the rates of diffusion or effusion for
two gases using the formula:
Thanks
