Thermal equilibrium

One of those PPTs I used for my FORMAL observation. Enjoy! -_-'

1. THERMAL EQUILIBRIUM Lesson #4

2. Objectives Define thermal equilibrium

3. Solve sample problems involving thermal equilibrium

4. Apply thermal equilibrium in daily life

5. Toon Tales What’s the title of the lesson again, Sheldon? Mrs. Puff, can we go back to the 1 st slide?

6. Quiet now children! So before we begin, eyes on the board please. Study the illustration.

7. A thermometer is placed on the forehead of a kid with a fever. 98 °F After 30 seconds The thermometer reads 98 ° F

8. The thermometer was not removed until the time reached 5 minutes. 101 °F After 5 minutes The thermometer now reads 101 ° F

9. Why did the temperature change after some time? Easy! Because they’re not yet in thermal equilibrium! Bu..Bu..But.. I, I can’t understand! Why?!

10. What!? Remember? When two substances having different temperatures are introduced or kept together, heat flows from a substance at higher temperature to a substance at lower temperature .

11. To make it more correct, heat continues to be transferred until their temperatures are equalized . When this stage is achieved, only we can say that we can say that the substances are in thermal equilibrium .

12. Oohh .. So that explains why the liquid inside the thermometer rises as time passes by. Yes! That is why we need to wait for a few minutes before taking the reading of the thermometer.

13. Of course. With that, the kid’s body and the thermometer will reach the same temperature Hey! You keep on finishing my sentences! Why are you late anyway? So what? I already understand the lesson.

14. You… you!!!!! Darn! You’ll pay for this!!! You’ll see! One day, I will beat you!! Whatever. Timmy. Holy!! My water is now getting warmer! Help me Timmy!!!

15. Don’t worry doggy, we’ll get you some ice for you later Really? Thanks He he he … They don’t know I have fairy godparents! But I wonder how many ice will make the juice cold again?

16. COSMO!!! WANDA!!! Where are you guys!?!?

17. But it seems that you lost your magic powers.. Timmy needs help… ..and equipped only with the knowledge of thermal equilibrium. How are you going to help him?

18. First you need to consider the condition of Doggy’s drink. T i = 15 °C m = 200 g How much ice would be enough to cool down the temperature of the water? (mass) T f = 10 °C

19. The mixture of ice and water would eventually reach thermal equilibrium. However, they must be in a closed system so that heat will completely transfer from one body to another.

20. Or simply, it must follow the Law of Conservation of Energy Δ E = 0 No heat will flow out of the system

21. Q + Q = 0 Q lost + Q gained = 0 Q gained = - Q lost (w here Q = mc Δ T) negative denotes heat released

22. Can you solve the problem of Timmy? Do you now have what it takes? Well then, let us see if you can use your skills in problem solving. Or do you wish to give up?

23. T i = 15 °C m = 200 g T i = 0 °C m = ? T f = 10 °C MIXED

24. Q gained = - Q lost mc Δ T = - (mc Δ T) m i c i ( Tf-Ti i ) = - [ m w c w ( Tf-Ti w )] “ i ” subscript for ice “w” subscript for water

25. A 200 g sample of water at 353 K is mixed with 200 g of water at 283 K. What is the final temperature of the mixture?

26. Test Yourself

27. 3. A 100-g Aluminum block at 373 K is placed in 100 g of 281 K water. The final temperature of the liquid is 298 K. What is the specific heat of aluminum?