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26 Cards in this Set

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  • Back
kinetic-molecular theory
describes the behavior of gases in terms of particles in motion

- small particles
- sep. by empty space
- particles are far apart so no significant attractive or repulsive forces
- particles in constant, random motion
- move in straight lines until they collide w/ walls or other particles
elastic collision
one in which no KE is lost (nature of collisions between gas particles)

- KE can be transfered, but the total KE of the 2 particles does not change
= (0.5)(m)(v^2)

- m = mass of particle
- v = velocity (speed and direction of motion)
the measure of the average KE of the particles in a sample of matter

at a given temp, ALL gases have the same average KE
the movement of one material through another

- the random motion of gas particles causes them to mix until evenly distributed
Graham's law of effusion
the rate of effusion for a gas is inversely proportional to the square root of its molar mass

- also applies to diffusion

effusion- when a gas escapes through a small opening
force per unit area

gas particles exert pressure when they collide w/ the walls of their container
an instrument used to measure atmospheric pressure

the height of the mercury is determined by:
- gravity exerting a constant downward force
- an upward force is exerted by air pushing up
an instrument used to measure gas pressure in a closed container

a flask is connected to a U tube that contains mercury
- the difference in the height of the mercury in the 2 arms is used to calculate the pressure of the gas in the flask
pascal (Pa)
the SI unit of pressure

1 Pa = 1 N/m^2
atmosphere (atm)
unit often used to report air pressure

1 atm = 101.3 kPa
Dalton's law of partial pressures
each gas in a mixture exerts pressure independently of the other gases present

Def: the total pressure of a mixture of gases = the sum of the pressures of all the gases in the mixture
partial pressure
the portion of the total pressure contributed by a single gas
depends on:
-number of moles
-size of container
-temp of mixture
NOT on identity of the gas b/c at a given temp and pressure, the partial pressure of 1 mole of any gas is the same
3 intermolecular forces:
- dispersion forces
- dipole-dipole forces
- hydrogen bonds
dispersion forces
weak forces that result from temporary shifts in the density of electrons in electron clouds
- dominant force of attraction between identical nonpolar moleculars
- exist between all particles but only play a role when no other forces are present
- temporary
- occur by random chance when electron distribution is uneven
- between molecules held together by nonpolar covalent bonds
dipole-dipole forces
- stronger than dispersion forces
- occurs between polar covalent molecules (which contain permanent dipoles)

neighboring polar molecules orient themselves so that the opp. charged regions correspond
hydrogen bond
a dipole-dipole attraction that occurs between molecules containing a hydogen atom bonded to a small, highly electronegative atom w/ at least 1 lone electron pair

- hydrogen MUST be bonded to either a fluorine, oxygen, or nitrogen atom in order for a hydrogen bond to occur

- stronger than typical dipole-dipole forces
properties of liquids
- tightly packed particles

- can be compressed (but change is volume is small)

- a fluid

- can diffuse through another liquid but does so more slowly than gases b/c intermolecular attractions interfere

- volume is fixed---individual liquid molecules do not have fixed positions but intermolecular forces limit their range of motion

-takes the shape of their container
a measure of the resistance of a liquid to flow

determined by:
1. type of intermolecular forces involved
- >attractive force = >viscosity

2. shape of the particles
- shorter, more compact molecules = lower viscosity

3. temp.
- decreases with increases in temp. (increases in temp = increases in average KE, more energy makes it easier for the molecules to overcome intermolecular forces)
surface tension
the energy required to increase the surface area of a liquid by a given amount

a measure of the inward pull of particles to the interior

- stronger attractions between particles = greater surface tension
compounds that lower the surface tension of water

also called surface active agents
the force of attraction between identical molecules
the force of attraction between molecules that are different
properties of solids
- strong attractive forces limit the motion of the particles of vibrations around fixed locations in the solid

- more densely packed than liquids

- ordinary amounts of pressure will not change volume
crystalline solid
a solid whose atoms, ions, or molecules are arranged in an orderly, geometric, 3-d structure
unit cell
the smallest arrangement of connected points that can be repreated in 3 directions to form the lattice