Download PHASES OF MATTER

PHASES OF MATTER
I. Temperature & Phases:
A. The average KE of a substance is called
the temperature … and is measured by a
thermometer.
I. ↑E…↑T… ↑ motion …gases/plasma
II. ↓E…↓T… ↓ motion …solids
B. Absolute Zero: the temperature in which
there is NO molecular motion
• Not yet been reached
• Basis of the Kelvin scale (no negative E
values)
• Is –273.15°C (approx. –273 °C) or
0K
II. Solids
A.
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General information:
Particles are in a relatively fixed position
Particles are vibrating
Lowest KE
Particles are arranged in a definite pattern
Have a definite volume
Have a definite shape
B.
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Crystal patterns:
Most simple pattern is called a unit cell
3D arrangement is called a crystal lattice
Solid substances fit 3 general patterns:
1. Isomorphous: one structure
ex. NaCl
2. Polymorphous: many structure
ex. CaCO3
3. Amorphous: no regular structure
…has irregular MPs
ex. Glass, coal
ISOMORPHIC SOLID…SODIUM
CHLORIDE CRYSTALS
POLYMORPHOUS SOLID…CALCIUM CARBONATE
C. Hydrates: solid crystals with water
trapped in the lattice
• Physical appearance is often different than
the anhydrous crystal
• Ex. CuSO4-5H2O
• Decrepitance: the “popping” created by
trapped water turning into gas as a
hydrated crystal is heated
D. Deliquescence: solids that dissolve when
exposed to atmospheric moisture
• Ex. CaCl2 & MgCl2
BLUE: hydrated copper (II) sulfate
III. Liquids:
A.
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General information:
Particles have more KE than solids
Have a definite volume
Assume the shape of their container, up to
their volume line
Fluidity (flows)
Viscosity: resistance to flow
Liquid
Liquid
VISCOSCITY
B. Vapor: gas escaping above a liquid
• Leads to vapor pressure
• Amount of liquid/vapor depends on
LeChatelier’s Principle
“if a stress is placed on a system, the
system will adjust to reduce the stress”
C. Evaporation…change from L→G that occurs at
any temperature
• Occurs ONLY at the surface
• Liquid molecules build up enough E to escape
the surface
• Factors that increase evaporation rate:
1. Surface area
2. Remove the vapor (wind, fan)
3. Increased temperature
• Volatility: liquids that evaporate readily at
room temperature
…ex. Alcohols, gasoline
VOLATILITY
D. Water…the “freak”
• Liquid water is in a Bent geometry, while
ice is linear…liquid water takes up less
volume …more dense
…solid water floats on liquid water
• Most dense temp. is 4 °C
• Ice is linear & polar, and forms a crystal
lattice
• Density: L>S>G
• < 4 °C is more dense than > 4 °C
• Cohesion: water is bonded to another water
by H-bonds…weak
…leads to Surface Tension: top surface of
water is bonded together
…water droplets stay together
• Adhesion: water is attracted to other
substances
…leads to Capillary Action (Imbibition)
…water “climbs” against gravity
…water dissolving substances
Cohesion
SURFACE TENSION
IV. Gases
General information:
• Particles have much more KE than liquids
• Particles are independent of each other
• Random motion of particles…leads to many
collisions (no loss of E)
• Infinite volume (will expand) – called expansion
• Can be compressed – volume is decreased and
particles move close together
• Assumes the shape and volume of their container
• Fluidity
V. Plasma
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Plasma: When gases reach a very high
temperature and become ionized (charged)
> 5000 °C
Violent collisions (knocks electrons free)
Plasma “vapor” is made of electrons and
positive ions
Majority of the universe (stars, Sun, lightning)
Has magnetic properties
Fluidity
VI. Phase Changes
A. Phase Change: when matter changes
from one state to another
• Is a physical change
• Involves a change in energy (heat content)
• Endothermic: heat is put into the system
(required)
• Exothermic: heat is released
B. Phase Changes:
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Fusion (melting)…S→L…endo
Crystallization (freezing)…L→S…exo
Vaporization (boiling)…L→G…endo
Condensation …G→L…exo
Sublimation…S→G…endo
ex. Dry ice, solid deodorant
Deposition… G → S…exo
Sublimation of Dry Ice
C. Temperatures:
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Boiling Point (BP): temperature in which
a substance changes from a L→G
…opposite of the Condensation Point
Melting Point (MP): temperature in
which a substance changes from a S→L
…opposite of the Crystallization Point
Normal BP: BP at 1 atm of pressure
D. Triple Point: the temperature and
pressure at which all 3 phases of a
substance may coexist in a
thermodynamic equilibrium
VII. Energy - Heat of Phase Changes
• Physical changes (ex. phase changes) are always
accompanied by energy changes. Most common form of
energy change involves heat. Heat is defined as the
energy transferred as a result of a temperature
difference. Heat is measured in a unit called a joule (J).
• Conversion Factors
1 cal = 4.184 J
1000 cal = 1 Cal (these are food calories)
1 kcal = 1 Cal
• Energy…measured in calories (cal) in metric and
joules (J) in SI.
Ex. 1 How many Joules are in
4.58x1024 cal?
Ex. 2 How many Joules are
in 285 Calories (candy bar)?
Ex. 3 How many calories are in
6.20x1012 J ?