Download Phases of Matter and Phase Changes

Phases of Matter, Energy
and Phase Changes
Phase of Matter

.
Depends on
strength of forces
of attraction
between particles.
Solids

Definite shape and volume.
Most dense phase (Exception is water!)
Difficult to compress.
Particles vibrate in fixed positions
Crystalline lattice structure.
Most attraction between particles.

Note:

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Amorphous solids include glass,
plastic, wax, and silly putty
Liquids




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Definite volume
No definite shape
Hard to compress
Particles slide past each
other
Forces of attraction
between particles still high
Gases


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
No definite shape or volume
Expands to fill container
Lowest density
Little attraction between
particles
“Vapor” = a gaseous state of
something that is normally liquid

(Ex: water vapor)
Changes in Phase
Gas
Condensation
Vaporization
(Boiling or Evaporating)
Liquid
Solidification
Melting (fusion)
Solid
Phase Changes
Short Summary video on phases: (1 min)
http://www.youtube.com/watch?v=s-KvoVzukHo&safe=active
Applet: (Excellent)
https://phet.colorado.edu/en/simulation/states-of-matter
http://www.harcourtschool.com/activity/states_of_matter/
Let’s Skip a Phase

Sublimation

Directly from the solid
phase to the gas phase.

Happens with substances
with weak intermolecular
forces of attraction

They separate easily!

Ex: CO2(s) dry ice, Iodine
CO2(s) → CO2 (g)
http://www.youtube.com/watch?v=8tHOVVgGkpk
Energy

Energy = capacity to do work or produce heat.
It can be anything that causes matter to move or
change direction.

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Many different types of energy
Ex: electrical, thermal, atomic, mechanical
“Chemical” energy is the potential energy stored in
the bonds between atoms
Law of Conservation of Energy

Energy can’t be
created or
destroyed, just
transferred from
one form to another
PE vs. KE

Potential Energy
stored energy


Energy can be stored in
bonds between atoms
Kinetic Energy
energy of motion

All atoms are moving
and vibrating unless at
absolute zero
Energy and Changes to Matter

Exothermic Change:


A + B → C + D + energy
Energy is released or “ex”its
Endothermic Change: A + B + energy → C + D

Energy is absorbed or “en”ters
Energy During Phase Changes

Solid
Liquid or Liquid
Gas
Endothermic
 Energy is absorbed and overcomes attractive
forces between particles

Add heat

Gas
Liquid, Liquid
Solid
Exothermic
 As particles come closer together energy is
released

Remove heat
Heat Energy

Also called Thermal energy, it makes particles
move more as it is added

Measured in Joules or calories.
http://www.youtube.com/watch?v=f1eAOygDP5s&safe=active
Heat Flow or Transfer

Heat energy
travels from an
object of higher
temp. to one of
lower temp. until
both reach the
same temp.
Temperature

Measure of the average kinetic energy
(motion) of all the particles in a sample.

Not a form of energy!!!

But if you add heat energy or take it away, it
causes particles to move faster or slower and
thus changes the temp.
Heat vs Temp.
https://www.youtube.com/watch?v=yxBTE
MnrZZk
Heat vs. Temperature

Teacup vs. Bathtub

Both at 25˚C

Which one contains
more heat energy?

Which one has the
greater average KE?
Temperature Scales Used in
Chemistry
Celsius
 Fixed points of scale based on the freezing
point and boiling point of water

0 °C = water freezes, 100 °C = water boils
Kelvin
 Scale based on lowest temperature possible

0 K = absolute zero
https://www.youtube.com/watch?v=-G9FdNqUVBQ
Temperature
Scales and
Conversions
K = ˚C + 273
Absolute Zero

Temperature at which particles have
slowed down so much they no longer
possess any kinetic energy.
0 Kelvin
-273° Celsius
Heating & Cooling Curves

Graphically represents temp. changes as heat
energy is added or taken away.
Label This Graph
Interpreting the Graph

The slanted portions =
temp is changing
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Single phase is heating
up or cooling down
KE is changing
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The flat portions =
temp not changing

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Substance undergoing
a phase change
PE is changing
Heating Curve for Water
What is Melting Pt? Boiling Pt?
Heat Equations

Calculates the energy involved when a
substance changes in temperature or
undergoes a phase change.
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Use this when temperature of substance
changes use this formula:
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When Undergoing Phase Change use one of
these formulas: TEMPERATURE CONSTANT
Q
= mHf
Use when changing from
solid to liquid (melting) or
liquid to solid (freezing)
Q
= mHv
Use when changing from
liquid to gas (vaporization) or
gas to liquid (condensing)
Physical Constants for Water
Table B
Use these constants in Heat Equations
Hf = heat of fusion = 334J/g
Hv = heat of vaporization = 2260J/g
Specific Heat Capacity (“c”) = 4.18 J/g x K
What is Specific Heat Capacity?
Specific Heat: “c”
Joules of heat needed to raise 1 gram of a
substance 1°C.

Substances have different abilities to absorb
heat when energy is applied depending on
their composition.
Ex: Piece of Iron vs. Water.
Calorimeter

Instrument to determine amount of heat lost or
gained in a reaction by measuring changes in the
temp. of water surrounding the system.
Virtual Calorimetry
http://group.chem.iastate.edu/G
reenbowe/sections/projectfolder
/flashfiles/thermochem/heat_me
tal.html
Q = mcΔT
Multi-step Heat Problems (Honors)

Need to use more than one of the heat
equations and add up the total heat.

Note: Specific Heat of different phases of water!
= 2.10 J/gx°C
 H2O (l) = 4.18 J/gx°C
 H2O(g) = 1.84 J/gx°C
 H2O(s)
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Ex: Calculate the heat energy to raise 10
grams of water at -25°C to 80°C.
Draw a heating curve. Figure out # of steps.
 1.) Heat ice from -25° to 0°
q = mcΔT
 2.) Melt ice to liquid at 0°
q = mHf
 3.) Heat liquid water from 0° to 80° q = mcΔT
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Heat Lost = Heat Gained (Honors)

When two objects of different temperatures
are placed together in a closed system,
heat flows from hotter to colder object until
they reach same temperature.
mcΔT = mcΔT

Total heat lost = total heat gained
Try This!!

Online App Demonstrates Specific Heat
and Calorimetry

http://elearning.classof1.com/demo/2D_Lab/Chemistry/specificHeat/
specificHeat.html