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Chapter 13
Chapter 13
Essential Questions:
1. What are the nature of gases,
liquids and solids?
2. How can you describe changes
between the states of matter?
3. Predict changes of state based
on physical conditions.
Tiny particles in all
forms of matter are
in constant motion
Kinetic energy(KE):
the energy that a
particle has because
of that motion
•A gas is composed of particles
(atoms or molecules)
•A gas in a container will fill the
container, no matter the shape.
•Uncontained gases diffuse into
space.
•The particles of a gas move
rapidly, in constant random
motion •
•Particles travel in straight
paths until they hit one another
or another object
•All collisions are perfectly
elastic
•KE is transferred from one
particle to another.
•Total KE remains the same.
Caused by the collision
of gas particles with
an object
In a vacuum there are
NO gas particles present
therefore
NO collisions resulting in
NO pressure
Results from the
collisions of air
molecules with
objects
Decreases as you
go up a mountain
because air layer
thins at high
elevations
Used to measure
atmospheric
pressure
Remember:
1 atm = 760 mm Hg = 101.3 kPa = 760 torr
A gas is at a pressure of 1.5 atm.
Convert to kPa and mm of Hg
1.5 atm
1
101.3 kPa
1atm
1.5 atm 760 mm Hg 1140 mm Hg
1 1 atm
151.95 kPa
What does the blue curve
represent?
What does the red curve
represent?
In which sample is the
average KE of the particles
high?
Temperature KE
Absolute zero= 0 K = -273°C
KE = 0
Distribution of KE
in cold water
Distribution of KE
in warm water
Hot water
Liquids and gases
FLOW.. they are
fluids
Liquids have a
stronger
attraction
between particles
Liquids are denser
then gases
Pressure on a liquid
there is very little
effect on the
volume
Liquids and solids are condensed states of matter
•Water molecules at
the surface of the
liquid break away
converting to a gas
or vapor
•Particles vaporize and collide
with wall of lid or containers
• then create vapor pressure
above liquid
•some molecules condense
back into a liquid
Evaporation is a cooling process
(like when you sweat)
because molecules with highest KE (highest
temp) escape, leaving behind the slower
(cooler) molecules.
Measure of the force exerted
by a gas above a liquid
Dynamic equilibrium
rate of evaporation = rate of condensation
Temp of contained liquid
vapor pressure
Measures vapor pressure of a liquid
Temperature @ which vapor pressure of liquid
= external pressure
Normal boiling point: boiling point at 101.3 kPa
(1atm)
Why does it take longer to cook food in water
at high altitudes? Atmospheric pressure decreases with altitude,
decrease pressure,
so water boils at lower temp.
lower temp means longer to cook
What is the boiling point of chloroform at 101.3
kPa?
What is the vapor pressure of ethanol at 40°C?
About 20 kPa
60°C
Less KE
Particles are closer together
Attractive forces between molecules are
stronger (than in liquid or gas)
Melting point: temperature @ which a
solid changes into a liquid
Atoms, ions or molecules arranged in
an orderly repeating 3D pattern
Ionic compounds:
higher melting point
strong attractive
forces
Molecular compounds:
lower melting point
held together by
weaker force
2 or more different molecular forms
of the same element
Ex: Glass, rubber, plastic,
asphalt
i.e. Glass has cooled to a
rigid state without
crystallizing.
Glass is sometimes
called a super-cooled
liquid.
Lack an ordered internal structure
The change of a substance
from a solid to a gas or vapor
with out passing through the
liquid state
The line
between
each phase
represents
when the 2
phases
occur at
equilibrium
Triple point:
the place
where all 3
phases can
exist in
equilibrium
with
one another
Kinetic Energy
Kinetic Theory
Gas Pressure
Vacuum
Atmospheric Pressure
Barometer
Absolute Zero
Evaporation
Vaporization
Vapor Pressure
Boiling Point
Normal Boiling Point
Melting Point
Crystal
Unit Cell
Allotropes
Amorphous Solid
Sublimation
Phase Diagram
Triple Point
Ionic compounds:
higher melting point
strong attractive
forces
Molecular compounds:
lower melting point
held together by
weaker force
