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Thermal Energy Transfer Conduction, Convection and Radiation
Thermal Energy Transfer
Conduction, Convection and Radiation
New Unit Tab
• Get a black color tab from the front table
• Use the next clean page in your journal and title it:
Thermal Energy Transfer
Questions to answer
What you should be able to explain by the end of today:
1. What is heat?
2. How does thermal energy move through matter?
3. How is heat transferred by conduction, convection and radiation?
Questions to Ponder
1. What is heat?
2. Where does it come from?
3. How does heat move?
Want to see something cool?
Heat Demonstration
• http://www.youtube.com/watch?v=Ci5P5yy0xlg
• http://www.youtube.com/watch?v=xPl3foajmcw
Now let’s learn more about heat.
• First we are going to make a foldable
• Pick up a piece of white copy paper
• Follow instructions on the next slide
To Make Foldable: 1. On the short side of the paper, fold it down an inch.
2. Now fold it in half, hamburger style.
3. Now fold it in thirds. You should have 3 same sized sections
Conduction
Convection
Radiation
Th
erm
al E
ne
rgy
Definition Examples
Definition Examples
Definition Examples
Outside of Foldable Inside of Foldable
The Movement of Heat • Thermal energy is the energy of heat, which
moves from a warmer object to a cooler object. This is known as thermal transfer.
How is Heat Transferred?
• There are THREE ways heat can move.
– Conduction
– Convection
– Radiation
Conduction • Conduction is the transfer of heat that occurs
when two objects of different temperatures touch.
• Heat is transferred from one particle of matter to another in an object without the movement of the object.
• In other words, the heat
moves from molecule to
molecule within MATTER!
Have you ever…
• Touched a metal spoon sitting in a pan of boiling water only to be surprised by hot HOW it is??
Think back to what you know about metals and nonmetals. What conducts heat better, metal or nonmetal? Why?
Here is how Conduction works: • Think of a metal spoon in a pot of water being heated.
• The fast-moving particles of the fire collide with the slow-moving particles of the cool pot.
• Because of these collisions, the slower particles start to move faster and heat is transferred.
• Then the particles of the pot collide with the particles in the water, which collide with the particles at one end of the spoon.
• As the particles move faster, the metal spoon gets hotter. This process of conduction is repeated all along the metal until the entire spoon is hot.
Examples of Conduction
• A piece of metal in a forge glows red as heat is transferred to the metal from the forge.
• Now the warmer object is the hand and it’s heat transfers to the cooler ice cube, eventually causing it to melt.
Windows in your house
What is the path of conduction of a window?
CONVECTION • Convection is the transfer of heat within fluids or air
(gas).
• Heat is transferred by currents within the fluid or gas
• Convection=VENTS through air and liquid particles
• Convection moves in a circular pattern.
Examples of Convection: • Have you ever noticed that the air near the ceiling is
warmer than the air near the floor? Or that water in a pool is cooler at the deep end?
• Examples: air movement in a home, pot of heating water.
• Pick one of these examples and draw the circular pattern in your notes.
Convection on Earth
• Convection currents cause the cooler breezes you experience by a large body of water.
• These currents also cause the movement of magma within the earth.
RADIATION • Radiation is the transfer of energy by
electromagnetic waves.
• Radiation does NOT require matter to transfer thermal energy (it occurs in space).
It does not ONLY come from the sun.
Radiation comes from other sources Have you ever sat too close to a campfire while
cooking marshmallows– enjoying the warmth-- only to notice that your skin is really warm?
Examples of RADIATION
1. Fire
2. Heat Lamps
3. Sun
When does heat transfer stop ? • Thermal energy movement will continue to move from
one object to another until all objects have reached the same temperature.
The ice cools down the water, and then as it sits in the room, the warm air causes condensation. Eventually, the ice melts, but the water is still cooler than the air. What happens if that water is left out long enough? It becomes the same temperature as the air.
Conductors and Insulators
Conductor – easily transfers heat.
• Why are cooking pots good examples?
Insulator – doesn’t easily transfer heat.
• Why is this coat a good example?
Show what you know!
• Examine each picture
• Discuss with your table group what type of heat transfer you see.
• Write your answer on the white board and hold it up when done.
• Ready?
Picture A • Examine the photo, then identify the type of
heat transfer on the white board.
Picture B
• Examine the photo, then identify the type of heat transfer on the white board.
Picture C • Examine the photo, then identify the type of
heat transfer on the white board.
Your foldable should be complete
• Glue it into your journal, be sure you can open the foldable!
