STATES OF MATTER AND

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STATES OF MATTER AND Powered By Docstoc
					KINETIC MOLECULAR
     THEORY

GAS PRESSURE AND
     VOLUME
   Section 11.1
   Section 11.2
SECTION
  11.1
STATES OF MATTER: REVIEW
                 SOLIDS
•   Tightly packed particles
•   Crystal lattice
•   Definite shape and volume
•   Limited to NO movement
•   Affected by gravity
                LIQUIDS
• More loosely packed particles
  (than solids)
• Take the shape of container
   or vessel
• Move with vibrational and
  rotational energy
• Affected by gravity
                  GASES
• Particles move independently
  of one another
• High degree of disorder
  (bumping into each other)
• Vibrational, rotational AND
  translational energy
• Flow in all directions
  – Not affected by gravity
• Expand to fill the volume
  of a container
   THE KINETIC MOLECULAR
      THEORY OF GASES
The theory makes these assumptions:
• Gas particles have virtually no volume (mostly
  empty space in a container of gas)
• Gas particles have no attraction/ repulsion to
  each other
• Gas particles have rotational, vibrational and
  translational movement
• Their kinetic energy is DIRECTLY related to
  temperature (higher temp = higher Kin energy)
• This is the description an “IDEAL GAS”
         IDEAL GASES

 “An ideal gas takes up
 hardly any space and the
 particles do NOT attract
 each other”
- In reality, no gas is really ideal
SECTION 11.2
        CLOSED SYSTEM
• How do gases behave in a closed
  system?
• A CLOSED SYSTEM contains constant
  moles of a substance
• It is not open to the atmosphere
• Examples:
  – CO2 in a fire extinguisher
  – O2 in a oxygen tank
  FACTORS THAT AFFECT
         GASES
• Temperature (T)
• Pressure (P)
• Volume (V)
          PRESSURE (P)‫‏‬
• Force exerted per unit of surface area


                            f
• Common Units:          P
  – Pascals (Pa)‫‏‬
  – Kilopascals (kPa)‫‏‬
                            A
  – atmosphere (atm)‫‏‬
  – Torr (Torr)
  – mm Hg
     PRESSURE OF A GAS
• Not measurable like pressure of a solid
  or liquid
• Pressure of gas is determined by
  kinetic motion of molecules
• Ex:
  – when filling a basketball with air, more
    molecules collide with inside of basketball
  – The total number of collisions and the
    strength of the force = total gas pressure
     PRESSURE OF A GAS
         continued…
• As gas molecules
  collide with sides
  of a container
  they exert a
  force.
• These exert a net
  force or pressure
  on the container.
   Standard Atmospheric pressure
• The column of air above one square meter at sea
  level and 0°C is 101.3 kPa
  – See pg 425, Fig 11.9
• Equivalent to:
  – 760 mmHg
  – 760 Torr
  – 1 atm
• Or, 101.3 kPa = 760 mmHg= 760 Torr= 1 atm
• To convert between each: (use ratios!  )
  – Ex: Convert 100kPa to torr
     100.0 kPa x 760.0 torr = 750.2 torr
                  101.3 kPa
           BOYLE’S LAW:
• Explains the relationship between pressure
  and volume
• "The volume of a given gas is inversely
  proportional to pressure"
• Temperature must remain constant for this
  to occur

    V 1P1  V 2 P2
  (1 = initial,   2   = final)
BOYLE’S LAW
          EX: BOYLE’S LAW
    Ex: A balloon has a volume of 4.50 L at
    room temperature but when the
    pressure is increased to 110.2 kPa. What
    will its final volume become?

•   P1 = 101.3 kPa
•   V1 = 4.50 L
•   P2= 110.2 kPa
•   V 2= ?
        BOYLE'S LAW problem
             continued…
   V 1P1  V 2 P2
  (4.50L) (101.3 kPa) = V2 (110.2 kPa)
    V2 = 4.137 L

To Check:
• the unit for answer is in L (volume)
• when units cancel out only L should remain
• the volume of the balloon has decreased due to
  increase in pressure
       HOMEWORK

• Page 423 # 1,2,4,5,6,7
• Page 435 # 1,3,4,5

				
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