1. Heat Transfer

2. Conduction Heat transfer via particle collision. via = “by way of”
particle = electron
normally occurs between solids that are in direct contact with each other
Question for thought:
Why do pots and pans have a wooden or plastic handle?

3. Conduction Good Conductors: solids with loosely held electron
ex) metals (silver is the best conductor)
Poor Conductors:
(AKA: Insulators)
solids with firmly held electron
slows down conduction in either direction, but does not stop conduction.
ex) wood, air (thermal underwear)

4. Convection Heat transfer via movements of fluids.
expansion and cooling
occurs between liquids or gases
denser (cooler) fluids go to the bottom
less dense (warmer) fluids move to the top
Question for thought:
Why does air become warm when pumping up a bike tire?
speed up air molecules = temp increase

5. Convection atmospheric convection produces winds Lakeshore winds:
Daytime: ground warms faster than water leads to sea breeze from water.
Night: ground cools faster than water (warmer) leads to breeze out to sea.
land
land

6. Gas Relationships Temperature increase  volume increase
Pressure increase  volume decrease
Density increase  volume decrease
Remember when an object is heated, temperature goes ___ so molecules move _____. The results is a _______ volume otherwise known as ______ ________. up
faster
larger
thermal expansion

7. Radiation Heat transfer via radiant energy.
Energy travels from the Sun to the Earth with no material in between.
Radiant energy is electromagnetic energy (or electromagnetic waves).

8. Radiation Frequency is directly related to temp.
Frequency is how often a wave occurs.
High frequency = short waves = high temp
Low frequency = long waves = low temp

9. Radiation All materials emit radiation…but they also absorb radiation.
Good emitters are good absorbers
Black in color
Feels warmer
Poor emitters are poor absorbers
White in color
Feels cooler
At constant temp emission = absorption

10. Radiation Terrestrial radiation Energy emitted by the Earth
Infrared or heat radiation
Source: radioactive decay in the Earth

11. Radiation Since radiation is a wave, radiation has wave properties
Reflection
Not all radiant energy will reflect some will absorb.

12. What heat transfer process is used?
Boiling water on a stove top
conduction
Heating your house
convection
Green house effect
radiation
Lake turnover

13. What heat transfer process is used?
Heat lamp or camp fire for warmth
radiation
Wind
convection
Sunlight heating the Earth
Electric blanket
conduction

14. Is energy transfer a perfect process?No
Energy conversion is not 100% efficient.
Most energy is lost in the form of heat.