I. States
of Matter
–Kinetic Molecular Theory
–States of Matter
A. Kinetic Molecular Theory
• KMT
– Particles of matter are always in motion.
– The kinetic energy (speed) of these particles
increases as temperature increases.
– Kelvin Temperature scale represents the relationship
between temperature and average kinetic energy.
• K = °C + 273
• 10 °C = _________ K
• 23 °C = _________ K
• 200 K = _________ °C
Evaporation
• the conversion of a liquid to a vapor
below its boiling point
• What happens…
– Molecules at the surface of the
liquid go into the vapor state
Boiling
• the conversion of a liquid to a vapor
at its boiling point
• What happens…
– Molecules of water vapor form at
the bottom and rise to the surface
Phase Changes
• Melting/Freezing
• Vaporization/Condensation
• Sublimation: Change of a substance from a solid to
a gas or vapor w/o passing through the liquid state
– Examples: dry ice, iodine
• Deposition: Change of a substance from gas to
solid w/o passing through the liquid state
Phase diagrams
• Triple point: temperature
and pressure at which all
three phases are in
equilibrium.
• Critical Point: temp. and
pressure past which the
liquid and gas phases
cannot be distinguished
between
Heating Curves
Gas - KE 
Boiling - PE 
Liquid - KE 
Melting - PE 
Solid - KE 
Heating Curves
Copyright 1999,
PRENTICE HALL
Chapter 11
10
Heating Curves
• Phase Change
– change in Potential Energy (molecular arrangement)
– temp remains constant until the phase change is
complete
• Molar Heat of Fusion (Hfus)
– energy required to melt 1 mole of a substance at its
melting point
– Melting is an endothermic process
– + ΔH
Heating Curves
• Molar Heat of Solidification
– ΔHsolid
– Energy released when 1 mole of a substance
changes from liquid to solid
– Exothermic process; -ΔH (heat released)
– Heat lost is equal to heat gained during melting
Heating Curves
• Molar Heat of Vaporization (Hvap)
– energy required to boil 1 mole of a substance at its
boiling point
– Endothermic; +ΔH
Heating Curves
• Molar Heat of Condensation
– Heat released when one mole of a substance changes
from gas to liquid
– Exothermic; -ΔH
– Heat released is equal to the heat gained during boiling
– Ex. Steam burns
Practice Problems
• How much heat (kJ) is needed to melt
17.0 g of Na? (∆Hfus = 2.60 kJ/mol)
• 1.92 kJ
• Given that the molar heat of vaporization
of oxygen is 6.82 kJ/mol, how much
energy (kJ) would be needed to vaporize
100.0 g of liquid oxygen?
• 21.31 kJ
• How much heat would be released when
85.0 g of oxygen gas condenses?
• (∆Hvap oxygen is 6.82 kJ/mol, so then what
is ∆Hcondensation)
• -18.1 kJ
Example
(Heat of combustion)
• The standard heat of combustion (∆H°rxn) for
glucose (C6H12O6) is -2808 kJ/mol. If you eat
and burn 70.g of glucose in one day, how much
energy are you getting from the glucose?
– Step one: convert g of glucose to moles
• 70. g glucose x 1 mol = 0.28 mol glucose
1
246 g
– Step two: Use (∆H°rxn) to find amount of kJ released
• 0.28 mol glucose x -2808 kJ = -790 kJ released
1
1 mol
– Step three: if glucose released -790 kJ, then YOU
GAINED +790 kJ of energy