Transcript 3 Types of Heat Transfer

3 Types of Heat Transfer
6th Grade
1) Why are some of Earth’s layers
solid and others liquid?
2) Why doesn’t the Earth melt?
3) Why do Earth’s layers change?
The magic answer: HEAT TRANSFER!
• What is a good definition for Heat Transfer?
Heat Transfer:
Remember this rule: Heat
always moves from a
warmer substance to a
cooler substance
• (ex. holding an ice cube
will make your hand
begin to feel cold in a
few seconds.)
• What are the 3 types of
Heat Transfer?
Heat Transfer:
• 1) Radiation
• 2) Conduction
• 3) Convection
What type of heat transfer is
Radiation?
1) Radiation
• The transfer of energy through space
• Happens with no direct contact between a
heat source and an object
• What are examples of radiation?
Examples of Radiation:
• Sunlight is radiation that warms the Earth’s
surface
• When you feel heat from a fire without
touching the flames
What type of heat transfer is
Conduction?
2) Conduction:
• Heat transfer between materials that are
touching
• What are examples of Conduction?
What are examples of Conduction?
• Example: When you walk barefoot on hot
concrete
• Example: When a hot pot of water heats up a
metal spoon.
• Example: A cold cast iron skillet is placed onto a
stovetop. When the stove is turned on, the skillet
becomes very hot due to the conduction of heat
from the burner to the skillet.
What are examples of Conduction?
• A cube of ice is placed into your hand. Over
time, heat conducted from the your hand to
the ice cube will cause the ice to melt.
• When an athlete warms sore muscles with a
heating pad
What are examples of Conduction?
• When a piece of hot lasagna is placed onto a
porcelain plate, the plate will feel warm to the
touch after several minutes due to the
conduction of heat from the just-cooked food to
the plate on which it sits.
• A shirt is placed on an ironing board to be ironed.
Heat from the iron is conducted to the shirt,
making it easy to iron out all those unsightly
wrinkles and make the shirt look sharp.
What type of heat transfer is
CONVECTION?
3) Convection
• Movement of currents within a fluid
• When a liquid or gas is heated, the particles
expand, or become less dense and rise
• When particles cool, they become more dense,
and sink back to the bottom
• This creates continuous convection cycles
What are the three important things to
remember that cause convection
cycles to happen?
Convection is caused by:
• Heating and cooling of the fluid
• Changes in the fluid’s density
• The force of gravity
During the convection cycle, as the
warm particles expand and rise to the
top, is the density of these particles
increasing or decreasing?
Density is decreasing because as the
particles get warmer, they expand
(take up more room) and therefore
become less dense.
As particles cool down, is the force of
gravity stronger or weaker?
As particles cool down, their density is
increasing, so the force of gravity is
stronger.
Remember that objects that are more
dense have a higher gravitational pull .
Which cylinder has a higher density?
Answer –the one on the right. It has
more tightly packed particles.
• Warmer particles become LESS dense because
the same number of particles expand (are
farther apart) and take up more space
Where in the Earth’s interior does
convection occur?
Answer: THE MANTLE
Remember our study of the Sun?
The same thing is happening in the
Earth’s mantle
Earth’s Mantle
• As the core heats the lower mantle (which is
solid), it becomes less dense so rises through the
Asthenosphere to the Lithosphere
• The Lithosphere is cooling and becoming more
dense, so it sinks into the Asthenosphere
• This is a continuous process –Convection Cycle
• These convection cycles happen over millions of
years
Examples of heat transfer by
Convection:
Examples of heat transfer by
Convection:
• Heating a pot of water over a flame
• Cold air from an open freezer sinking to the
floor