Unit 2: Kinetic Molecular Theory
E.Q. How are solids, liquids and
gasses different in terms of
energy?
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The 3 states of matter are affected by 3
factors
1. The space between particles.
2. The motion of the particles
3. The energy of the matter.
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Solids can be described as
• Particles very close together
• Particles move very slowly and vibrate in place
• Lowest amount of energy
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Liquids can be described as
• More space between particles than solids
• Able to move around each other
• More energy than solids but less than gases.
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Gases can be described as
• Particles very far apart.
• Move very rapidly.
• Highest amount of energy.
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Kinetic Molecular Theory (KMT)
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Matter is made of tiny particles in constant motion
As energy is added particles move faster
In the gas phase there is no attraction between particles.
Pressure of a gas is caused by the collisions of particles
with the wall of the container.
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Unit 2 : Properties of Gases
• EQ Explain how gas pressure is affected by particle
collisions.
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• Compressibility: a measure of how much the volume of
matter decreases under pressure.
• Gases are easily compressed because of the space
between the particles. (remember KMT)
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Factors Affect Gas Pressure
1. Amount of Gas: by adding gas you
increase the particles and number of
collisions so the pressure increases, and
vise versa.
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2. Volume of Gas: by increasing the
volume you increase the space that the
particles can move in. Thus the pressure
decreases as the number of collisions
decreases, and vice versa.
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3. Temperature: as the temperature
increases the kinetic energy of the particles
increases and they hit the walls of the
container and each other with more energy,
increasing the pressure, and vice versa.
Warm temp.
Hot temp.
Cold temp.
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Pressure units:
kpa, atm, mmHg, psi, torr
101.3 kPa = 1 atm or
1atm = 760 mmHg or
101.3 kPa = 760 mmHg
STP Standard Temperature and Pressure
the values are 0°C and 101.3 kPa or 0°C and 1.0 atm
or 0°C and 760 mmHg
Volume units : mL or L
Temperature units : C° or K
However all calculations must have temperature in
Kelvin when working gas law problems
To change C° to Kelvin : C° + 273 = K
To change Kelvin to C° : Kelvin – 273 = C°
Absolute zero all molecular motion stops. 0 Kelvin
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The Gas Laws
• Boyle’s Law: If the temperature is
constant, as the pressure of a gas
increases, the volume decreases.
P1V1 = P2V2
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• Charles Law: As the temperature of an enclosed gas
increases, the volume increases, if the pressure is
constant. Temperature must be in Kelvin. ◦C + 273 = K
or V1T2 = V2T1
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• Pressure vs Temperature Law: As the
temperature of an enclosed gas increases,
the pressure increases, if the volume is
constant. Temperature must be in Kelvin.
◦C + 273 = K
or P1T2 = P2T1
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• The Combined Gas Law: all three gas
laws combined. Temperature must be in
Kelvin. ◦C + 273 = K
or P1V1T2 =P2V2T1
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