states of matter

1. States of matter & the kinetic
molecular theory.
Matter is classified into 3 states or phases:
Solids, liquids & gases
The structure, arrangement
& movement of the particles
determines the state of the
substance.
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2. Diffusion & Brownian motion
Diffusion and Brownian motion in liquids
and gases, provides proof of the
existence of particles in matter.
Diffusion is the movement of
particles from a region of high
concentration to lower concentration -
until there is even distribution of particles
throughout the gas or liquid.
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3. Brownian motion is the haphazard,
random motion of larger particles that
are being bumped by much smaller gas
or liquid particles – ones that can’t even
be seen under a microscope.
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4. Forces between particles
There are forces between the particles in
each of the states of matter.
Solids – strongest forces – vibratory
motion & held close together.
Liquids – weaker forces – further apart
& able to flow past one another
Gases – weakest forces – particles far
apart & move easily
in all directions
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5. Phase changes
Matter can change from one state to
another by adding or removing energy –
usually in the form of heat.
Solid to gas – sublimation
Solid to liquid – melting
Liquid to gas – evaporation
Gas to liquid – condensation
Liquid to solid – freezing
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6. Temperature & Phase changes
The temperatures at which phase
changes take place have specific
names:
Solid → liquid – melting point
Liquid → gas – boiling point
Gas → liquid – condensation point
Liquid → solid – freezing point
The state of a substance at a certain
temperature, is determined from its
melting or boiling points. 6

7. Temperature & Phase changes
H2O at -5 0C means it is in the solid state
(ice) – since it is below the freezing point
of 0 0C.
H2O at 120 0C means it is in the gaseous
state (steam) since it is above its boiling
point of 100 0C.
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8. Common melting & boiling points
Substance Melting point Boiling point
Water 0 0C 100 0C
Nitrogen -210 0C -196 0C
Oxygen -219 0C -183 0C
Diamond 3 550 0C 4 830 0C
Carbon dioxide -79 0C -57 0C
Ethanol -114 0C 78 0C
Copper 1 083 0C 2 600 0C
Mercury -39 0C 357 0C
Table salt 801 0C 1 413 0C
Iron 1 536 0C 3000 0C
Sodium 98 0C 892 0C
Lead 327 0C 1750 0C
Ammonia -78 0C -33 0C
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9. Heating curve for water:
This graph shows how the curve changes
during the phase changes & heating process.
Temperature
Time
0C
-10 0C
100 0C
M.P.
B.P.
ICE
WATER
STEAM
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10. Kinetic molecular theory
This theory explains properties of solids,
liquids & gases, relative to the particles
making up matter & their movement.
Particles in each phase are in constant
motion and thus have a kinetic energy.
Particles move at different speeds, but at
the same temperature, they have the
same average kinetic energy.
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11. Kinetic molecular theory: solids
Solids have:
 strong forces between particles
 a size & shape
 vibrate about a fixed point
 repulsive forces – thus no compression
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12. Kinetic molecular theory: liquids
Liquids have:
 weaker forces of attraction
 move more freely past each other
 no fixed shape – shape of container
 particles have different velocities
 ave. Ek same throughout liquid
 strong repulsive forces – no
compression
 particles collide with each other &
walls of container – thus a pressure.
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13. Kinetic molecular theory: gases
Gases have:
 weak forces between particles
 greater motion & thus more energy
 random motion with elastic collisions
causing pressure
 no repulsive forces – particles far
apart – easy to compress
 particles move at different
speeds but ave. Ek is the
same.
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