chapter 15 kinetic theory
TRANSCRIPT
INTERMOLECULAR FORCES•Account for:
•surface tension•capillary action•Melting/boiling points
Bond Type IMF Strength State of Matter
Ionic Electrostatic forces
Extremely strong b/c attracting opposite
chargesSolids
PolarCovalent
Hydrogen bonding
Strong b/c of large electronegativity
differenceLiquids
Dipole-dipole
Medium b/c of polarity (partial charges)
NonpolarCovalent
LondonDispersion
Forces
Weakest b/c no charges Gases
INTERMOLECULAR FORCES
•Account for:•surface tension•vapor pressure•capillary action•chromatography•Melting/boiling points
THE NATURE OF GASES
•The word “Kinetic” means motion•The energy an object has due to its motion is called kinetic energy
•The kinetic theory states that tiny particles in all forms of matter are in constant motion!
3 BASIC RULES OF THE KINETIC THEORY FOR GASES:
1) Gas is made of particles (usually molecules/atoms)
• Small, hard spheres• Insignificant volume• Relatively far apart from
each other• Little/No attraction or
repulsion between particles
3 BASIC RULES OF THE KINETIC THEORY FOR GASES:
2) Particles in a gas move rapidly in constant random motion• Move in straight paths• Change direction only when colliding
with something else• Average speed of O2 in air at 20oC is
an amazing 1660 km/h!
3 BASIC RULES OF THE KINETIC THEORY FOR GASES:
3) Collisions are perfectly elastic• meaning kinetic energy is transferred
without loss from one particle to another• the total kinetic energy remains constant• no energy is lost between particles• bounce off each other without sticking
GAS PRESSURE- defined as the force exerted by a gas per
unit surface area of an object• Due to:
a) force of collisions b) number of collisions
What about when NO particles are present?• Then there cannot be any collisions, and
thus no pressure called a vacuum
GAS PRESSURE
Atmospheric pressure is the amount of force the weight of the atmosphere exerts per square inch• Decreases as you climb a mountain
because the air layer thins out as elevation increases
Barometer is the measuring instrument for atmospheric pressure; dependent upon weather
STANDARD TEMPERATURE AND PRESSURE (STP)
For gases, it’s important to relate measured values to standards:•Standard conditions for gases are a temperature of 0oC and a pressure of 1 atm