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# Convection and Heat Transfer

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## Josh Patrick

on 29 April 2014

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#### Transcript of Convection and Heat Transfer

Heat Transfer & Convection Currents
I can explain how heat is transferred.
I can explain how convection currents form.
I can describe convection currents in the mantle.
I Can Statements
Bell Ringer
Hold an ice cube in your hand for one minute. Observe what happens.
Is heat moving from the ice cube to your hand or is heat moving from your hand to the ice cube? Why?
What are three ways that heat is transferred?
radiation, conduction, and convection
Heat always moves from a warmer substance to a cooler substance.
I can describe convection currents in the mantle.
Describe radiation.
Radiation is the transfer of energy through space.
There is no direct contact between the heat source and an object.
What are some examples of radiation?
Heat from the sun
Heat you feel around a flame.
Heat you feel from a lamp.
Describe conduction.
Heat transfer within a material or between a heat source and an object.
What are some examples of conduction?
Heat transfer by touch!
JUST REMEMBER...
Heat from the flame transfers to the pot when pot is placed on flame.
Heat is transferred from the coffee cup to the persons hand.
Heat from soup is transferred to spoon and from the spoon to his hand.
Heat from the sand is moved to feet.
How are you experiencing heat transfer right now?
Describe Convection Currents.
Describe convection.
What happens to particles of an object when they are heated?
The speed up, vibrate and bump into other particles causing them to heat up also.
Convection is heat transfer by the movement of currents within fluid (liquids or gases).
During convection, heated particles of fluid begin to flow. The flow transfers heat from one part of the fluid to another.
How does heat transfer by convection occur?
Convection is caused by differences in temperature and density within a fluid.
when a liquid or gas is heated, the particles move faster and spread a part. As a result, the particles of heated fluid occupy more space. The fluid's density decreases. BUT when a fluid cools, its particles move more slowly and settle together more closely. As the fluid cools, its density increases.
How does the density of most substances change when the substance is heated?
The density decreases because the molecules move further apart.
Why do less dense substances rise?
Gravity pulls everything towards the center of the Earth. Denser material is pulled harder, forcing less dense material upward.
What is a current?
A Constant Flow!
A convection current is the flow that transfers heat within a fluid (liquid or gas).
Heating and cooling of the fluid, changes the density and the force of gravity to set the currents in motion.
CONVECTION CURRENTS CONTINUE AS LONG AS HEAT IS ADDED!
How could you stop a convection current?
Describe Convection Currents in the Mantle.
Heat from the core and mantle cause convection currents in the mantle.
Many geologists think that hot mantle rock rises from the bottom of the mantle to the top. The hot rock eventually cools and sinks back to the bottom. This cycle continues over and over.
Convection Currents also occur in the outer core. These convection currents cause Earth's magnetic field.
What are some examples of heat transfer by convection?
Why do you think heating units or vents are best located near the floor?
So that heat rises throughout the whole room.
Explain how each is an example of heat transfer.
Pair-Up and discuss the question.
Full transcript