1. ENERGY

2. IRP Binders & Log Books Name on log book Name(s) on binder
Rubric clipped to contents page
Log book(s) placed into binder
Stack binders NEATLY (turn opposite directions) at designated location for your class.

3. Whiteboard Icy Hot Lab Conclusion Questions
Group F #1
Group E #2
Group D 3 i
Groups C & G #4 – Region A
Group B #4 – Region B
Groups A & H #4 – Region C

4. Changes to Calendar!
ALL ISEF Forms (if they are not in your binder) – due 9/23
Unit 3 WS1 is not due Monday
We will discuss Energy Bar Charts on Monday
Icy Hot Lab (due 9/24)

5. ENERGY substance-like quantity present in every system of particles
always involved when a system undergoes change

6. ENERGY in a system: Thermal -- energy of motion (“Eth account”)
depends on mass and velocity of particles
temperature of a system is a measure of how fast particles are moving
Phase -- energy due to arrangement/orientation of particles which have an attractive force between them (“Eph account”)
attractions lower energy of a system
solids have lowest Eph, liquids have greater Eph, and
gases have the greatest Eph

7. ENERGY in a system:
Energy can be transferred between “accounts” within the system of particles OR
Energy can be transferred into or out of a system of particles
A change in temperature or phase is observable evidence of transfer of energy

8. TRANSFER OF ENERGY between the system and the surroundings
Heating – transfer of energy through collisions of particles
Working – transfer of energy when macroscopic objects exert forces on each other
Radiating – transfer of energy by the emission or absorption of light

9. LAW OF CONSERVATION OF ENERGY
Energy can not be created or destroyed
Total amount of energy remains the same during all energy transfers

10. HEAT AND TEMPERATURE
Heat is a measure of energy transferred into or out of a system through collisions of particles
Temperature is a measure of how fast the particles are moving

11. MEASURE OF TEMPERATURE
Celsius Scale
freezing point of water is set at 0oC
boiling point of water is set at 100oC
interval between them is divided into 100 parts
Kelvin Scale
absolute zero – theoretically the lowest possible temperature  particles stop moving
absolute zero = 0 K = oC
the size of each degree (interval) is the same as Celsius

12. Icy Hot Lab –copy notes into lab notebook
Changes in physical arrangement of particles
Energy used to break attractions between particles of solid
Both solid & liquid present
Temperature A
Time (Energy)

13. Icy Hot Lab Changes in speed (motion) of particles
Energy used to speed up particles of liquid
Liquid only present
Temperature B
Time (Energy)

14. Icy Hot Lab Changes in physical arrangement of particles C
Energy used to break attractions between particles of liquid
Both Liquid & gas present C
Temperature
Time (Energy)

15. Icy Hot Lab “Report” Problem Question
Prediction graph (Title, axes labeled)
Copy of your actual graph, labeled according to data processing instructions
Answers to conclusion questions in complete sentences that stand alone.

16. Review of types of change – help for lab conclusions
Chemical change – a new substance is made
Physical change – no new substance made (phase change)

17. Energy Bar Charts – refer to Energy Bar Charts notes
How to represent the role of energy in physical change
© Modeling Chemistry 2007

18. Tracking Energy…
We were able to discuss how energy was transferred to the system (heating) and how the system responded (changes in particle motion or arrangement.
It would be helpful if we could keep track of how energy is transferred and stored.
Representation Tool = Energy Bar Charts.

19. Constructing an Energy Bar Chart
Consider the Lab
A beaker of liquid water is heated over a Bunsen burner.
1. Represent the process with a temperature – time graph. Then make an empty Energy Bar Chart

20. Constructing an Energy Bar Chart
2. Determine what is in the system
Write it in the center circle, which represents the system.
Everything else makes up the surroundings
WATERater

21. Constructing an Energy Bar Chart
3. Decide whether Ech is involved
In this case, you start with water and end with water; particles are not rearranged to form new substances
So, ignore Ech for now.

22. Constructing an Energy Bar Chart
4. Assign values to Eph
Due to interactions between particles, the energy stored due to the arrangement of particles is ranked: solids < liquids < gases
We choose to represent these phases by using:
Solids = 1 bar
Liquids = 2 bars
Gases = 4 bars

23. Constructing an Energy Bar Chart
Assign values to Eph
Use two Eph bars before and after
WATER

24. Constructing an Energy Bar Chart
5. Choose bars for Eth depending on
temperature
Use 2 bars for colder water and 4 bars for warmer water
Other values might also work; try to be consistent in your representations

25. Constructing an Energy Bar Chart
WATER

26. Constructing an Energy Bar Chart
6. Now show energy transfer using arrows showing energy entering or leaving the system.
Final situation has 2 more bars of E than initial; 2 bars had to be added to the system
Label the arrow using the symbol of the transfer mechanism.

27. Constructing an Energy Bar Chart
WATER Q
4 BARS
+ 2 BARS
6 BARS

28. Now, consider phase change
A tray of ice cubes (-8 ˚C) is placed on the counter and becomes water at room temperature
What do we know about the situation?
The system is the tray of ice cubes.
The solid water turns to liquid water - no change in Ech
The Eph increases (solidliquid)
The Eth increases (temp rises)
Now represent these changes using a temp/time graph and bar chart.

29. Initial & Final States
Choice of bars for Eth arbitrary, but keep consistent.
We used 2 bars for room temp and usually use 1 bar for “cold” substances.
Temp < 0˚C should be < 1 bar.

30. Account for Energy transfer
Energy must flow into system via heating