1. Chapter 22 Heat Transfer

2. 3 METHODS TO TRANSFER HEAT: ___________________ – All methods occur continuously and at the same time. http://t2.gstatic.com/images?q=tbn:ANd9GcQYXXMcH3Z45gYfE G7Qp0PU5Gg-Ejwkvktsr31uDZFybpXHHzB5ekDu1Kd_

3. CONDUCTION: _________________________ ________________________. The transfer of thermal energy is due to the collision of molecules between substances as well as intermolecular forces between molecules within a substance. Transfer continues until “thermal equilibrium” (same temperature) is reached for all materials. Heat flows from hot cocoa into and up the spoon as well as the cup.

4. Thermal Conductors: Solid materials conduct heat better than liquids and gases. ______________________ _____________________. ______________________ ______________________ _____________________.

5. INSULATORS: Poor conductors of heat. __________________________ __________________________. “cold” is the absence of heat. There is no transfer of “cold” on the transfer of loss of heat. Why are down jackets good insulators? – ____________________________ ___________________________.

6. What is the common insulating factor in each of these images? WOOL POLAR FLEECE FIBER GLASS

7. VACUUMS: Heat transfer in a vacuum cannot occur. Why not? – _______________________ _______________________ _____________________. Thermos bottles keep liquids warm because they are surrounded by a vacuum.

8. http://media.lonelyplanet.com/lpi/25100/25100-12/681x454.jpg What are some possible reasons that some roofs don’t have snow on them?

9. CONVECTION: _______________________ ______________________. Transfer of energy from one place to another through moving fluids (gases and liquids). _______________________ _______________________ ______________________.

10. DENSITY – mass per unit of volume Density = g/ml – When mass stays the same and volume increases due to expansion, density decreases. _________________________ ________________________. All materials try to reach “equilibrium” (density remains the same) The transfer of heat in a fluid causes a circulation (movement) of materials. D m V D m V

11. CONVECTION AROUND US: ________________ Sea breezes Land breezes ________________ https://encryptedtbn1.gstatic.com/images?q=tbn:ANd9GcQ7 uUnVIn157znDcxb424wEhQTXAcayKgO3dd2N4av_yB1TPp82A http://4.bp.blogspot.com/_vgawnhRg_KY/S43kondqO II/AAAAAAAACPY/EGsHyr42BrU/s400/convection.jpg

12. Based on your knowledge of convection currents, explain what is happening in the following diagram. Which is the “land’ breeze and which is the “sea breeze”. Why are the H (high pressure) versus L (low pressure) symbols located where they are? What is different between the daytime and nighttime image? What do you know about the specific heat capacity of water versus land? At about what time of day would the scenario on the left take place? What do you think the “relative” temperature of the land versus the water is in both scenarios?

13. http://www.nc-climate.ncsu.edu/secc_edu/images/sea_breeze.jpg

14. EXPLANATION FOR THE PREVIOUS SLIDE: _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

15. THERMAL(heat)RADIATION: The transfer of heat energy in the form of electromagnetic waves, including light. All substances above Absolute Zero (0 Kelvin) emit (give off) heat energy. Substances can also absorb (take in) energy.

16. Types of Waves Infrared waves: – Heat from a fire. Light Waves: – Visible form of radiant energy Radio Waves: – Transmit signals through the air. http://zebu.uoregon.edu/~imamura/122/images/electromagnetic-spectrum.jpg

17. http://lot.astro.utoronto.ca/images/spectrum.png

18. http://www.makingitmagazine.net/wp-content/uploads/2010/03/Zhengrong-Shi_suntech_solar.jpg INFRARED IMAGE OF EARTH

19. ABSORPTION and EMISSION: Substances that effectively absorb radiant energy also effectively emit (give off) radiant energy. __________________________ __________________________. The object will then emit more radiant energy in order to reach a “new thermal equilibrium”. Dark objects absorb and emit energy effectively. – Think about the temperature of pavement on a sunny summer day and a summer night. http://homtvnews.files.wordp ress.com/2012/07/kataro.jpg

20. ABSORPTION and REFLECTION: Energy is bounced back when reflected. _____________________ _____________________ ____________________. Think about wearing dark clothing versus wearing light colored clothing on a hot summer day. In which outfit would you remain cooler?

21. http://www.ashevillegeothermal.com/Solar_files/EarthAbsorption.jpg

22. http://www.global-greenhouse-warming.com/images/GreenhouseEffectDiagram.jpg

23. RATE OF HEAT TRANSFER: The transfer is always from hot to cold and is continuous until equilibrium is reached. The greater the difference in temperature, the faster the flow of heat. ____________________ – This is an “empirical relationship” – (based on observations) 98.6°F – average temperature of the inside of a human body. At 75°F, rate of heat flow out of your body matches the rate at which the body generates heat internally.

24. the end….©Kathleen Tringale