Kinetic-Molecular Theory Flashcards
Vapor
Gas produced from a liquid or solid under normal conditions (vapor pressure must be equal to that of the atmosphere)
Ideal gas
Imaginary gas that perfectly fits all of the assumptions of the kinetic-molecular theory. A gas that behaves independently of its environment (mostly noble gases and diatomic molecules)
Assumptions
A. Gases consist of a large number of tiny particles with much space in between
B. Collisions occur as elastic collisions, no net loss of kinetic energy
C. Gases are in constant, rapid, random motion
D. No attractive or repulsive forces between gases
E. Average kinetic energy is constant and depends on temperature
Johann van Helmont (1662)
Used “gas” to describe the most energetic phase of matter (derived from the Greek “chaos”, original matter on Earth)
Expansion
Allows gas to take the shape of the container
Pressure
Force per unit area
Barometer
Instrument to measure atmospheric pressure
Manometer
Instrument to measure pressure produced in a lab reaction or tank
Density
Measure of mass per volume (for gases g/l)
Diffusion of gases
Random spreading of gas in uniform dimensions
Effusion
Controlled escape of gas through a hole or pore
Condensation temperature
The point where gas molecules form a liquid
Real gases
Don’t behave completely according to the kinetic-molecular theory; intermolecular forces provide interactions that may change gas properties or behaviors
Van der Waal forces
General terms for weak intermolecular attractions between molecules
London dispersion forces
Caused by motion of electrons, increases as # of electrons increases. Can occur in any molecule to induce temporary polar behavior.
Dipole-dipole interactions
Electrostatic attractions based on distinct polarity of molecules
Hydrogen bonding
Hydrogen bonded to a highly electronegative atom is attracted to an unshared pair of electrons in a nearby molecule
Definite volume
Won’t expand, will take the shape of the container (liquid)
Incompressible (liquid)
Liquids equalize pressure, particles are close together
Fluidity
Ability to flow and be poured
Diffusion of liquid
Particles have motion and randomly spread, but more slowly than gases
Cohesion
Force of attraction between molecules of the same substance
Adhesion
Force of attraction between different substances
Surface tension
Force that pulls adjacent parts of a liquid’s surface together resulting in the smallest surface area possible
Capillary action
Attraction of the surface of a liquid to the surface of a solid; tends to move a liquid against gravity
Definite shape
Exists in a fixed form
Definite volume
All surfaces are free and defined