1. Laws of Thermodynamics: Too Hot, Too Cold, Just Right
Chapter 6, Section 7
Laws of Thermodynamics:
Too Hot, Too Cold, Just Right

2. HW: 6.7 PTG, pg. 676, #1-9 LO: SC: Do Now: Agenda:
Explain the 3 Laws of Thermodynamics as they relate to conservation of energy
SC:
Assess experimentally the final temperature when two liquids of different temperatures are mixed
Assess experimentally the final temperature when a hot metal is added to cold water
Calculate the heat lost and heat gained of two objects after they are placed in thermal contact
Discover if energy is conserved when two objects are placed in thermal contact and reach equilibrium temperature
Explain the concept of entropy as it relate to objects placed in thermal contact.
Do Now:
Write LO and SC on new left side page
WDYS/WDYT: pg 664
Agenda:
Do Now
Investigate
Summary

3. Investigate #1-3 #1-complete in your notebook
#2-3 Create a data table in your notebook to record all data.
#3 b-c Construct graph and use to answer questions

4. Investigate #4-5 Plan experiment, check procedures with teacher.
Conduct experiment

5. Investigate #6 Read Physics Talk, Specific Heat, pg 666-67
Complete #6 a-c

6. Summary
Discuss how this experiment proves the law of conservation of energy.

7. HW: 6.7 PTG, pg. 676, #1-9 LO: SC: Do Now: Agenda:
Explain the 3 Laws of Thermodynamics as they relate to conservation of energy
SC:
Assess experimentally the final temperature when two liquids of different temperatures are mixed
Assess experimentally the final temperature when a hot metal is added to cold water
Calculate the heat lost and heat gained of two objects after they are placed in thermal contact
Discover if energy is conserved when two objects are placed in thermal contact and reach equilibrium temperature
Explain the concept of entropy as it relate to objects placed in thermal contact.
Do Now:
What does Conservation of Energy mean to you? Explain your answer
Agenda:
Do Now
Physics Talk
Practice Problems
Summary

8. Physics Talk What did you observe in your experiment?
Equal amounts of hot and cold water produced a final temp half way between the initial temps of both
When you changed the amounts of hot or cold water the final temp was somewhere between the two initial temps, but closer to the temp of the water with the larger mass.

9. Physics Talk What is the Law of Conservation of Energy?
The total energy in a system is conserved, energy can neither be created or destroyed
Start=End
The cold water gained thermal energy through the transfer of heat, then the hot water must have lost and equal amount of thermal energy.

10. Physics Talk
What equation can we use to show the Law of Conservation of Energy?
Mass of water?
1mL=1g
50mL=50g

11. Physics Talk What is specific heat?
Energy is conserved whether the cool water is mixed with hot water or hot metal.
The heat energy (J) required to raise the temp of mass (1g) for a substance by 1°C.

12. Physics Talk
What is the equation for specific heat?

13. Physics Talk
Sample Problem

14. Physics Talk Conservation of Energy…Again!
Energy is not created or destroyed!
It can change from one from to another, but the total amount remains the same in a closed system!
Example: From GPEKE

15. Physics Talk
What is the difference between Temperature, Heat, and Thermal Energy?
Temperature is the measure of average kinetic energy of molecules.
High Temp--> more KE

16. Physics Talk
What is the difference between Temperature, Heat, and Thermal Energy?
Heat is the energy transferred from one place to another due to temperature differences.
Transfers from High heat to low heat

17. Physics Talk
What is the difference between Temperature, Heat, and Thermal Energy?
Thermal energy is a type of energy that results from the motion of atoms (related to temperature)
Increase thermal energy, increase temperature
Depends on the mass and temperature of the water
100g of hot water > 100g of cold water because of the difference in temp
A swimming pool with 10,000kg cold water > 1kg hot water due to mass

18. Physics Talk What is thermodynamics?
The study of the relationships between heat and other forms of energy transformation of one form into another.
There are 3 laws of thermodynamics.

19. Physics Talk Zeroth Law of Thermodynamics
If 2 objects have the same temperature as a third object, then the two objects must also have the same temperature.
If A=C, and B=C, then A=B

20. Physics Talk First Law of Thermo Dynamics
Conservation of energy related to hot and cold objects.
Hot Coffee (90°C) + Cold Milk (5°C) Coffee cools (10°C) slightly, Milk warms a lot (75°C)until they are at the same temperature (80°C)
Could be calculated with the equation if you know the mass of the coffee and milk.

21. Physics Talk Second Law of Thermodynamics
In irreversible processes, entropy or disorder always increases.
Time is irreversible
Thermal energy is transferred from hot objects to cold objects and NEVER goes from cold to hot spontaneously.

22. Physics Talk Second Law of Thermodynamics
Energy is only transferred from hot objects to cold objects until they reach an equilibrium temperature.
There is NO SUCH THING AS COLD ENERGY!

23. Physics Talk Second Law of Thermodynamics (con’t) Due to Entropy.
Related to the degree of disorder of molecules.
Solids are more organized (ordered) than liquids which are more ordered than liquids.
To go from solidliquidgas the object must gain thermal energy, increasing entropy.

24. Physics Talk
Example of Entropy

25. Checking Up Questions
Pg. 672, #1-4

26. Vocabulary Boxes
Complete for all vocab words in Chapter 6, Section 7.

27. Essential Questions Pg. 675 What does it mean? How do you know?
Why should you care?

28. Physics To Go
6.7 PTG, pg. 676, #1-9