Molecular Kinetic

1. Kinetic-Molecular
Theory
PREPARED BY: TYPE YOUR NAME HERE

2. S9MT -IIj - 20
 Investigate the relationship between:
 1 volume and pressure at constant
temperature of a gas
 2 volume and temperature at constant
pressure of a gas
 3 explains these relationships using the
kinetic molecular theory

3. Kinetic-Molecular Theory Postulates
1. Matter is made of particles
containing mass.
2. Particles of substances are in
constant, rapid, and random motion.
3. Collisions are either elastic or
inelastic.
4. Temperature measures average
kinetic energy.

4. Kinetic-Molecular Theory Postulates
5. Particles exert
intermolecular forces.
 These forces are “non-
existent” in gases.
 These forces are strong
in liquids and solids.

5. Comparing Two Theories
Atomic Theory
 Everything made of
particles
 All atoms of an element
are identical
 Atoms are neither created
nor destroyed
 A specific compounds has
the same ratio of atoms
Kinetic-Molecular Theory
 Particles have mass
 Particles are constantly
moving
 Particles collide
 Particles exert forces
 Temperature measures
kinetic energy

6. Postulate 1
 Matter is made of particles
containing mass. 1 AMU = 1.66054
x 10-24 g
Proton—1 AMU (1.0073)
Neutron—1 AMU (1.0087)
Electron—Without Mass (5.486 x 10-4
AMU)

7. Postulate 2
 Particles of substances are in
constant, rapid, and random
motion.
Motion has 3 characteristics
Constant
Rapid
Random

8. Postulate 3
 Collisions are either
elastic or inelastic.
1. Inelastic—loses energy (p.
421)
2. Elastic—doesn’t lose energy
(p. 421)

9. Postulate 4
4. Temperature measures average kinetic energy.
 Temp., Kinetic Energy
 Temp., Kinetic Energy

10. Quick Question
 After testing two unknown
substances A and B, you find
the boiling temperature for
substance A to be 20°C.
Substance B’s boiling point is
34°C. Which substance, A or B,
has stronger intermolecular
forces? Why?

11. Postulate 5
5. Particles exert intermolecular
forces.
 These forces are “non-existent” in
gases.
 These forces are strong in liquids and
solids.
 Dispersion Forces (London Dispersion)
 Dipole-Dipole Forces
 Ion-Dipole
 Hydrogen Bonding

12. Postulate 5—Dispersion
 Dispersion Forces
 Shape-induced charge (due
to asymmetry)
 Weakest force
 Exists on all molecules

13. Postulate 5—Dipole-Dipole
 Dipole-Dipole Forces
 Permanent dispersion force
(Causes asymmetry, which gives
rise to partial charges (-, +)
 Causes some molecules to be
polar
 Affects solubility

14. Postulate 5—Hydrogen Bonds
 Hydrogen Bonds
 Most important biologically
(induces protein folding)
 Assists in solubility
 Responsible for properties of
water
 Strongest force

15. Kinetic-Molecular Theory
(Gasses)
 Intermolecular forces “don’t
apply”
 Describe 4 variables
 Amount, volume, temperature,
pressure

16. Kinetic-Molecular Theory
(Gasses)
 Amount—given as n= mass/molar
mass
 Volume—given as L
 Temperature—given as K
 To convert °C to K, just add 273.15
 Pressure—given as atm or torr
(mm of Hg)

17. Kinetic-Molecular Theory
(Gasses)
 These variables lead to 4
relationships
 Boyle’s Law
 Charles’ Law
 Avogadro’s Law
 Dalton’s Law

18. Kinetic-Molecular Theory
(Gasses)
 Boyle’s Law
 P, V
 P, V

19. Kinetic-Molecular Theory
(Gasses)
 Pressure has several units
 1 atm
 760 mm Hg
 760 torr
 1.01325 x 105 Pa
 101.325 kPa

20. Kinetic-Molecular Theory
(Gasses)
 Charles’ Law
 T, V
 T, V

21. Kinetic-Molecular Theory
(Gasses)
 Avogadro’s Law
 If V, T, and P are held constant for 2 gases, then they
contain an equal number of particles.

22. Kinetic-Molecular Theory
(Gasses)
 Dalton’s Law
 If more than one gas is present, then the sum of the
pressures of all the different gasses equals the total
pressure.
 Pt = p1 + p2 + p3 + … + pn

23. Kinetic-Molecular Theory
(Gasses)
 Ideal Gas Law: PV = nRT
 R is a constant
 8.314 m3-Pa/mol-K
 0.08206 L-atm/mol-K
 62.36 L-torr/mol-K

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