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26 Cards in this Set
- Front
- Back
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kinetic-molecular theory
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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 |
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elastic collision
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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 |
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KE
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= (0.5)(m)(v^2)
- m = mass of particle - v = velocity (speed and direction of motion) |
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temperature
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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 |
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diffusion
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the movement of one material through another
- the random motion of gas particles causes them to mix until evenly distributed |
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Graham's law of effusion
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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 |
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pressure
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force per unit area
gas particles exert pressure when they collide w/ the walls of their container |
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barometer
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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 |
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manometer
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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 |
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pascal (Pa)
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the SI unit of pressure
1 Pa = 1 N/m^2 |
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atmosphere (atm)
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unit often used to report air pressure
1 atm = 101.3 kPa |
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Dalton's law of partial pressures
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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 |
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partial pressure
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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 |
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3 intermolecular forces:
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- dispersion forces
- dipole-dipole forces - hydrogen bonds |
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dispersion forces
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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 |
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dipole-dipole forces
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- 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 |
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hydrogen bond
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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 |
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properties of liquids
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- 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 |
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viscosity
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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) |
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surface tension
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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 |
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surfactants
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compounds that lower the surface tension of water
also called surface active agents |
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cohesion
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the force of attraction between identical molecules
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adhesion
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the force of attraction between molecules that are different
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properties of solids
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- 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 |
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crystalline solid
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a solid whose atoms, ions, or molecules are arranged in an orderly, geometric, 3-d structure
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unit cell
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the smallest arrangement of connected points that can be repreated in 3 directions to form the lattice
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