Gases
Kinetic-molecular Theory
Objects in motion have
energy called kinetic
energy.
The kinetic-molecular
theory describes the
behavior of matter in
terms of particle motion.
Gas particle size
Small particles that are separated from one
another by empty space.
The particles are small compared to the volume
of the space.
Gas particle motion
★ Gas particles are in constant random motion.
★ They move in a straight line until they collide with
other particles or with the walls of their container.
★ Collisions between gas particles are considered
elastic.
★ An elastic collision is one in which no kinetic
energy is lost.
Particle Energy
Two factors determine the kinetic energy of a particle:
1. Mass
2. Velocity
The kinetic energy of a particle can be represented by the
following equation:
Where:
KE-Kinetic energy
m- mass of the particle
v- velocity
TEMPERATURE IS THE
MEASURE OF THE
AVERAGE KINETIC ENERGY
OF THE PARTICLES IN A
SAMPLE OF MATTER!!!
Behavior of gases
Low density: There is a great
deal of space between gas
particles, so there are fewer
particles in a given area.
Compression and expansiongas can be compressed into
smaller volumes. It can also
spread out to fill larger volumes.
Diffusion
The random motion of gas particles cause gases
to mix.
Diffusion is the term used to describe the
movement of one material through another.
Example: When you’re cooking in the kitchen,
you can smell it through the house because the
gases diffuse.
Effusion
Effusion is when gas escapes through a tiny
opening.
★ This is what happens when you puncture
a tire.
Graham’s law- states that the rate of effusion is
inversely proportional to the square root of its
molar mass.
Lighter particles diffuse more rapidly than
heavier particles.
Gas pressure
Pressure is defined as the force per unit area.
A Barometer measures atmospheric pressure.
➔ The height of Mercury in a Barometer at sea level is 760
mm. This measurement is also called a Torr (for Torricellithe scientist who measured it.)
Manometer
Measures the pressure in a closed container.
Units of pressure
● Pascals
● Atmospheres- One atmosphere = 760 mm Hg or
760 Torr
Dalton’s law of partial pressures
States that the total pressure of a mixture of
gases is equal to the sum of the pressures of all
the gases in the mixture.