1. Heat
Heat Q is a transfer of energy from one object to another because it’s cooler. It’s not something an object “has” (we will call the energy inside an object its “internal energy”)

2. Heat Calories and Joules (James Joule 1849) 1 calorie = 4.186 J
Food calorie: 1 Cal = 1000 cal
Raising your 500 kg car with the energy in a large cream-filled 500 Cal donut: .
Compare to Empire State Building: 443 m

3. Specific heat
How much does T rise when heat energy is added? Typical specific heats Water 4186 Ice 2090 Steam 2010 Glass 840 Steel 500

4. Phase changes

5. Energy and phase changes

6. Latent heat during phase Changes
Water Latent heats L Ice melting/freezing 3.34 x 105 Water boil/condense 2.26 x 106

7. Latent heat during phase Changes
Which takes the most energy for the same quantity of H20?
melting ice at 0 C.
raising T from 0 to 100 C
boiling it

8. Calorimetry
Conservation of energy: +, – Q’s all sum to zero. or Q­gained by cold objects = Q­lost by hot objects (on both sides use positive quantities)
50 g of hot steel at 300 C is added to 100 g of water at 20 C. What is the final temperature? csteel = 0.12 cal/g/oC

10. Blackbody Radiation
blackbody: an object that when cool absorbs all light, and when hot, emits light in a spectrum that depends only on T.
Emissivity = 1 means perfect blackbody
emissivity e
Black paper
0.9
White paper
0.7
Anodized aluminum, Black
0.8
Aluminum highly polished
0.05

11. Blackbody spectrum, color

12. Radiated and absorbed power
Hot vacuum oven with a cold object inside
A piece of metal at room temperature (20 C) is put into a vacuum oven at 300C. What determines how fast its temperature rises?

13. Temperature of the earth:

14. P2. A rough black metal sphere is heated white-hot to 3000 K, and puts out 1000 W of radiation energy. If it is instead held at 1500 K, it will put out ______ W of radiation energy (ignore the T of the environment). A. 60 B. 250 C. 500 D. 750 E. 1000

15. P3. If instead the sphere is kept at 3000 K, but the radius of the sphere is doubled, it will put out ______ W of radiation energy. A. 500 B C D E. 8000

16. Thermal conduction Newton’s law of cooling Thermal conductivity
Highest for dense materials, metals

17. Typical thermal conductivities k [J/(smoC)]
Thermal conduction
Typical thermal conductivities k [J/(smoC)]
Copper 390
Steel (common) 80
Stainless steel 14
Glass 0.84
Wood 0.1
Air
Styrofoam 0.01
If air is great a insulator, why use fiberglass in houses, feathers in sleeping bags?

18. Our best insulators simply keep air from circulating!

19. Thermal convection

20. Thermal convection

21. P4. You put the end of a rod in the fire and the other end in a tub of water. The rod that would heat the water fastest will be _______
short and fat
long and fat
short and thin
long and thin