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kinetic molecular theory of matter
based on the idea that particles of matter are in constant motion
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ideal gas
a gas that fits all assumptions of the kinetic-molecular theory of gases
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what is the kinetic-molecular theory of gases based on?
an ideal gas
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5 major assumptions of an ideal gas:
- 1. gases consist of many tiny particles that are far apart (relative).
- 2. collisions between individual gas particles or between gas particles and the side of their container are totally elastic3. particles of gases are in constant, rapid, & random motion.
- 4. Gas particles don't attract or repel each other.
- 5. the average KE of gas particles depends on the temperature
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With the same number of atoms, the volume of a gas is
1000 times the volume of its liquid or solid
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Most of the volume of a gas is occupied by
empty space
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What kind of densitites do gases have?
Low- little mass per unit volume
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Elastic collisions
- there is no loss in the total KE of the system
- however, KE may be transferred from one particle to another
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What kind of charge do gas particles have?
neutral
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KE depends only on
- the velocity of the particle
- (atoms/molecules of the element/compound have the same mass)
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As temperature increases, velocity & KE
increase
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gases at the same temperature have the same
KE
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smaller particles with lower masses have what velocities?
higher
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large particles have what kind of velocities?
lower
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pressure
the force exerted per unit area on a surface
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the pressure exerted on a surface by a gas depends on the gases
- volume
- temperature
- number of gas molecules
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atomic presure is measured using a
barometer
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barometer invented by
Torricelli
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units of pressure
- 1. mm of Hg
- 2. 1 mm of Hg = 1 torr
- 3. At sea level O deg C, the avg atmosphere = 760 mm of Hg
- 4. 1 atmosphere (atm) = 760 mm of Hg
- 5. 1 atm = 101.3 kPa
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avg atmospheric pressure at sea level
760 mm of Hg
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gases are most commonly measure at
standard temperature and pressure (STP)
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At STP,
- temperature= 0 deg C
- pressure of 1 atm/101.3 kPa
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What is used to measure air pressure?
manometer
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Open manometer
air pressure pushes down on the column of Hg while the gas in the globe tries to push the Hg up
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closed manometer is another name for a
barometer
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In a closed manometer,
the tube isn't open and the area above the Hg is a vacuum, independant of atmospheric pressure
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particles of different substances at the same temperature have the same
KE
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what moves faster, smaller or larger particles?
smaller
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Absolute zero
- the temperature of a substance is lowered as far as it can be, and all motion ceases
- -237 deg C
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temperature can also be used to determine
the direction of the flow of energy
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energy flows from what to what?
warmer objects to colder ones
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heat
the amount of energy transferred between 2 objects at different temperatures. Measured in joules
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States of matter: gas
- particles are independant of each other
- far apart
- move in straight lines until they collide
- assume they shape and volume of their container
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States of matter: liquid
- particles are much closer than gas's
- far enough apart to slide past each other (flow)
- have definate volume, but take the shape of their container
- particles have vibratory motion around ever-changing points
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States of matter: solid
- particles are in fixed positions relative to neighboring particles
- fixed pattern- definite shape and volume
- particles have vibratory motion around a fixed point
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States of matter: plasma
- occurs when matter is heated to 5,000 deg C
- particles collide so violently that electrons are knocked off and these electrons and the positive ions that remain form plasma
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what do ionic compounds tend to be? why?
- crystalline solids
- very strong electrostatic forces holding the ions together
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molecular compounds are held together by
van der Waals forces
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if moleculare mass is high, the compiunds tends to be a
solid
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nonpolar molecules of low molecular masses tend to be
- gases
- HONClBrIF (except Br- liquid)
- CO2
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compiunds with high molecular mass and greaty polarity tend to be
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