Thermal Energy & Heat Temperature Temperature measure of the average KE (motion) of the particles.
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Transcript of Thermal Energy & Heat Temperature Temperature measure of the average KE (motion) of the particles.
Going from Celsius to Fahrenheit
oF = 9/5 (oC) + 32
Convert 37 oC to oF.oF = 9/5oC + 32oF = 9/5(37oC) + 32
= 66.6 + 32
= 98.6oF
Going from Fahrenheit to Celsius
oC = 5/9 (oF – 32)
Convert 68oF to oCoC = 5/9(oF – 32)oC = 5/9(68 – 32)
= 5/9(36)
= 20 oC
Thermal Energy
Thermal Energy the total energy of the particles in
a material (KE + PE) KE - movement of particles PE - forces within or between particles due to position
depends on temperature, mass, and type of substance
Thermal Energy
Which beaker of water has more thermal energy? B - same temperature, more mass
200 mL
80ºC
A400 mL
80ºC
B
Heat Transfer
Heat thermal energy that flows from
a warmer material to a cooler material
Heat is... measured in joules (J) a transfer of energy
Heat TransferWhy does A feel hot and B feel cold?
80ºC
A
10ºC
B
Heat flows from A to your hand = hot. Heat flows from your hand to B = cold.
Heat Transfer Heat is always
transferred from hot to cold.
Insulators slow the transfer of heat due to air pockets.
Conductors easily allow the transfer of heat, like metals.
Heat is transferred by radiation, conduction, and convection.
Radiation Transfer of heat
through electromagnetic radiation (light from stars or light bulbs).
Transferred in all directions.
No contact required! Dark or dull objects
absorb more than light or shiny objects do.
Conduction
Heat is transferred due to objects touching each other or through collisions.
Occurs best in solids. Heat continues to be
transferred until both objects reach the same temperature, called a thermal equilibrium.
Heat Transfer
Insulators slow the transfer of heat due to air pockets.
Conductors easily allow the transfer of heat, like metals.
Question???
Nick bought a bowl of soup in Styrofoam cup. He noticed that the metal spoon handle sticking out of the soup became too hot to touch, but he could hold the cup in his hand comfortably. Explain why the Styrofoam cup and spoon did not feel the same.
How did you do?
You should CORRECTLY use the following concepts: Molecules, Heat/Energy Transfer, Conductor, Insulator
The warmer molecules in the soup transfer heat energy to the spoon. The spoon is made of metal, a conductor, which allows the heat to move easily to your hand. The Styrofoam is an insulator, so the heat does not transfer to your hand easily.
Radiation vs. Conduction
1. Energy that travels as waves through space between things
2. Direct contact not necessary
3. From the Sun and light
4. Can travel through empty space
1. Energy that travels through contact of things
2. Contact is necessary
3. From faster moving molecules
4. Can’t travel through empty space
Conduction
Conduction is when energy transfers from one place to another by direct contact
Differential conduction is when energy transfers at different rates depending upon the material it is passing through
Differential conduction can explain these two mysteries
about the “Amazing Melting Ice Blocks”
1. Why does one block feel cold and one feel warm when they are the same temperature?
2. Why does the block that feels cold so much better at melting the ice than the “warm” block?
Convection
Transfer of heat through a liquid or gas through moving currents, called convection currents.
The cause of wind and weather.
The movement of a substance that is caused by differences in temperature and density.
EXAMPLES: wind boiling water
NATURE WANTS
EVERYTHING TO BALANCE ! !