Phases of Matter and Phase Change

Contributed by:

Jonathan James Fri, Jan 14, 2022 09:50 PM UTC

The highlights are:
1. Phases of matter
2. Change of phase
3. Energy
4. Energy during phase change
5. Heat flow and transfer
6. Heating and cooling curves
7. Heat equations
8. Specific heat capacity
9. Calorimeter

1. Phases of Matter, Energy
and Phase Changes

2. Phase of Matter
 Depends on
strength of forces
of attraction
between particles.

3. 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:
 Amorphous solids include glass,
plastic, wax, and silly putty

4. Liquids
 Definite volume
 No definite shape
 Hard to compress
 Particles slide past each
other
 Forces of attraction
between particles still high

5. Gases
 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)

6. Changes in Phase
Gas
Condensation Vaporization (Boiling or Evaporating)
Liquid
Solidification Melting (fusion)
Solid

7. 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/

8. Let’s Skip a Phase
 Sublimation
 Directlyfrom 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

9. Energy
 Energy = capacity to do work or produce heat.
It can be anything that causes matter to move or
change direction.
 Many different types of energy
 Ex: electrical, thermal, atomic, mechanical
 “Chemical” energy is the potential energy stored in
the bonds between atoms

10. Law of Conservation of Energy
 Energy can’t be
created or
destroyed, just
transferred from
one form to another

11. PE vs. KE
 Potential Energy
stored energy
 Energy can be stored in
bonds between atoms
 KineticEnergy
energy of motion
 Allatoms are moving
and vibrating unless at
absolute zero

12. 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

13. Energy During Phase Changes
 Solid Liquid or Liquid Gas
 Endothermic
 Energy is absorbed and overcomes attractive
forces between particles
Add heat

14.  Gas Liquid, Liquid Solid
 Exothermic
 As particles come closer together energy is
released
Remove heat

15.

16. 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

17. Heat Flow or Transfer
 Heat energy travels
from an object of
higher temp. to
one of lower temp.
until both reach
the same temp.

18.

19. Temperature
 Measure of the average kinetic energy
(motion) of all the particles in a sample.
 Not a form of energy!!!
 Butif 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=yxBTEMnrZZk

20. Heat vs. Temperature
 Teacup vs. Bathtub
 Both at 25˚C
 Whichone contains
more heat energy?
 Which one has the
greater average KE?

21. Temperature Scales Used in
Chemistry
 Fixed points of scale based on the freezing
point and boiling point of water
0 °C = water freezes, 100 °C = water boils
 Scale based on lowest temperature possible
0 K = absolute zero
https://www.youtube.com/watch?v=-G9FdNqUVBQ

22. Scales and
K = ˚C + 273

23. Absolute Zero
 Temperatureat which particles have
slowed down so much they no longer
possess any kinetic energy.
0 Kelvin
-273° Celsius

24. Heating & Cooling Curves
 Graphically represents temp. changes as heat
energy is added or taken away.

25. Label This Graph

26. Interpreting the Graph
 Theslanted portions =  Theflat portions =
temp is changing temp not changing
 Single phase is heating  Substance undergoing
up or cooling down a phase change
 KE is changing  PE is changing

27. Heating Curve for Water

28. What is Melting Pt? Boiling Pt?

29. Heat Equations
 Calculates
the energy involved when a
substance changes in temperature or
undergoes a phase change.
 Usethis when temperature of substance
changes use this formula:

30.  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)

31. 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

32. 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.

33. 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
Q = mcΔT

34. Multi-step Heat Problems (Honors)
 Needto use more than one of the heat equations and
add up the total heat.
 Note: Specific Heat of different phases of water!
H O(s) = 2.10 J/gx°C
2
H O (l) = 4.18 J/gx°C
2
H2O(g) = 1.84 J/gx°C
 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

35.

36. 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

37. Try This!!
 Online App Demonstrates Specific Heat
and Calorimetry
 http://elearning.classof1.com/demo/2D_Lab/Chemistry/
specificHeat/specificHeat.html

Book a Trial Class

Download