1. Science 10 Mr. Jean April 25 th, 2012

2. The plan: Video clip of the day Physics test etc… Thermal Energy Thermal Energy Calculations

3. Physics Test People who have not written their science test need to do so. Alex B, Taylor M, Morgan J, Nathaneal G, Travis S and Alex S.

4. Color of emission

5. Solar Energy:

6. Energy in the Atmosphere:

7. The process of atmospheric scattering causes rays of sunlight to be redirected to a new direction after hitting a particle in the atmosphere. In this illustration, we see how three particles send light rays off into three different directions. Scattering does not change the striking light ray's wavelength or intensity.

8. Atmospheric absorption. In this process, sunlight is absorbed by an atmospheric particle, transferred into heat energy, and then converted into long wave radiation emissions that come from the particle.

9. Atmospheric reflection. In this process, the solar radiation striking an atmospheric particle is redirected back to space unchanged.

10. Sunlight reaching the Earth's surface unmodified by any of the above atmospheric processes is termed direct solar radiation. Solar radiation that reaches the Earth's surface after it was altered by the process of scattering is called diffused solar radiation. Not all of the direct and diffused radiation available at the Earth's surface is used to do work. As in the atmosphere, some of the radiation received at the Earth's surface is redirected back to space by reflection.

11. Temperature Scales: What is a thermometer?

12. Thermometers measure temperature. The first known accurate thermometer was invented about 350 years ago.

14. Triple Boiling Point of water

15. James Joule, 1818-1889 Image credit: Wikipedia

16. How does Energy effect matter?

18. The point of thermal dynamics (Study of “heat” energy) is really to do work. We know that heat is really a form of motion in particles and this motion can be used to produce energy.

19. Heat Engine Concept Any time a temperature difference exists between two bodies, there is a potential for heat flow Examples: –heat flows out of a hot pot of soup –heat flows into a cold drink –heat flows from the hot sand into your feet Rate of heat flow depends on nature of contact and thermal conductivity of materials If we’re clever, we can channel some of this flow of energy into mechanical work

20. Heat  Work We can see examples of heat energy producing other types of energy –Air over a hot car roof is lofted, gaining kinetic energy –That same air also gains gravitational potential energy –All of our wind is driven by temperature differences –We already know about radiative heat energy transfer –Our electricity generation thrives on temperature differences: no steam would circulate if everything was at the same temperature

21. How much work can be extracted from heat? ThTh QhQh QcQc  W =  Q h –  Q c TcTc Hot source of energy Cold sink of energy heat energy delivered from source heat energy delivered to sink externally delivered work: efficiency = =  W work done  Q h heat supplied conservation of energy Q

22. Let’s crank up the efficiency ThTh QhQh QcQc  W =  Q h –  Q c TcTc efficiency = =  W work done  Q h heat supplied Let’s extract a lot of work, and deliver very little heat to the sink In fact, let’s demand 100% efficiency by sending no heat to the sink: all converted to useful work

23. Thermal Energy Formula: Q = mc∆T Q = Amount of thermal energy (J) m = mass in grams (g) c = Specific heat capacity (J / g) T = Temperature change (ºC)

24. Specific Heat Capacities: Each substance has it’s own specific heat capacity. –For example water is 4.18 J/g * C.

25. Sample Question: If 1g of ethanol is burned to heat 100g of water, raising its temperature by 42K, how many energy was released by the ethanol?

26. The point of thermal dynamics (Study of “heat” energy) is really to do work. We know that heat is really a form of motion in particles and this motion can be used to produce energy.

27. Heat Engine Concept Any time a temperature difference exists between two bodies, there is a potential for heat flow Examples: –heat flows out of a hot pot of soup –heat flows into a cold drink –heat flows from the hot sand into your feet Rate of heat flow depends on nature of contact and thermal conductivity of materials If we’re clever, we can channel some of this flow of energy into mechanical work

28. Heat  Work We can see examples of heat energy producing other types of energy –Air over a hot car roof is lofted, gaining kinetic energy –That same air also gains gravitational potential energy –All of our wind is driven by temperature differences –We already know about radiative heat energy transfer –Our electricity generation thrives on temperature differences: no steam would circulate if everything was at the same temperature

29. How much work can be extracted from heat? ThTh QhQh QcQc  W =  Q h –  Q c TcTc Hot source of energy Cold sink of energy heat energy delivered from source heat energy delivered to sink externally delivered work: efficiency = =  W work done  Q h heat supplied conservation of energy Q

30. Let’s crank up the efficiency ThTh QhQh QcQc  W =  Q h –  Q c TcTc efficiency = =  W work done  Q h heat supplied Let’s extract a lot of work, and deliver very little heat to the sink In fact, let’s demand 100% efficiency by sending no heat to the sink: all converted to useful work

31. Try this: Using the table found on page 427 solve the following. 1) How much energy is used to heat 1000g of liquid water by 10 degrees? 2) If we put 1000J of energy into 500g of ethanol how much does it warm up by?

33. 1) How much energy is used to heat 1000g of liquid water by 10 degrees?

34. 2) If we put 1000J of energy into 500g of ethanol how much does it warm up by?