gases objectives: 1. state the kinetic theory of matter. 2. use the kinetic theory to explain states...
TRANSCRIPT
GasesObjectives:
1. State the kinetic theory of matter.
2. Use the kinetic theory to explain states of matter
Review/Preview
What is kinetic energy? Kinetic Molecular Theory applies to gases.
What would “kinetic-molecular” theory logically discuss?
The Kinetic-Molecular Theory
Def.: describes the behavior of gases in terms of particles in motion
Kinetic-molecular theory makes several assumptions about the size, motion, and energy of gas particles.
Kinetic-Molecular Theory Basic Assumptions :
1. Size: Gases are made of small particles separated by A LOT of empty space. This means the volume of the particles is
negligible; assume volume = 0. Because particles are so far apart, there is no
significant attractive or repulsive force between them.
Kinetic-Molecular Theory Basic Assumptions :
2. Motion: Particles are in constant, random motion, moving in a straight line until they collide with something. They can collide with the container walls or
with each other. Collisions with each other are considered to be
elastic collisions: a collision in which no kinetic energy is lost (but it may be transferred).
Kinetic-Molecular Theory Basic Assumptions :
3. Energy: Kinetic energy is determined by a particle’s mass and velocity (KE = ½ mv2)
Since temperature is a measure of the average kinetic energy of the particles in a sample of matter, then temperature is directly proportional to average kinetic energy of a gas sample.
What happens to temperature if particles in a sample slow down?
Why?
Review
Complete Workbook (p.73): 1-4 together as a class.
Explaining the Behavior of Gases
1. Low density (What is density?) – lots of empty space between particles
2. Compression and expansion - stress ball demo
Explaining the Behavior of Gases, continued……..
3. Diffusion and effusion What is diffusion? Def: the movement of one material through
another (examples: perfume, blood gases) Particles move from areas of high concentration
to areas of low concentration Lighter (less mass) particles diffuse more
rapidly
Explaining the Behavior of Gases, continued……..
3. Diffusion and effusion, continued…. Effusion: when a gas escapes through a tiny
opening (think punctured tire) Inverse (??) relationship between effusion
rates and molar mass So which gas would effuse (escape) faster,
ammonia (NH3) or hydrogen chloride (HCl)?
Gas Pressure
Pressure: force per unit area (psi or N/m2) When gas particles collide with a container wall, they
exert force, creating pressure. Air pressure = column of air pushing down on the
ground. Why is air pressure lower at the top of a mountain than
it is at sea level? SI unit for pressure: pascal (Pa) = 1 N/m2
Others: 1 atm = 760 mm Hg = 760 torr = 101.3 kPa
Assignment
Workbook (p.73): 5-12 together Problem-Solving Lab (p.390)