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Transcript of Thermal Energy
By Tyler Seawright
What Does That Mean?
In order for thermal energy to transfer, you must have two things that are both not the same temperature.
Used for transferring thermal energy in a gas or liquid
In the picture, hot molecules move up and cold move down.
What is the point of the fins or heat sinks on this oil heater?
To cool it off
What is Thermal Energy?
Thermal energy is heat or how hot something is.
There is no such thing as cold.
Cold is just what we call when something has less thermal energy.
The energy is made from moving atoms
The Condition for Heat to Transfer
In order for heat to transfer, there must be a difference in two temperatures.
Ways Heat Can Tranfer
Conduction is the process by which heat energy is transmitted through collisions between neighboring molecules.
Like the picture with the ice cube in a hand the ice is in contact with the hand
In conduction the substance with less thermal energy gains energy and the object with more energy loses energy.
Lets Go Back to That Ice Cube
If you are holding ice,
then you are voluntarily letting the ice suck the heat out of your hand.
What is going on in this picture?
One Practice Problem
1. You pull one 70° Fahrenheit bottle of soda out of your garage for a drink. You pour the soda into a glass and add three 20° ice cubes to it. Name every time heat was transferred from the garage to your mouth.
Keep in mind that air and hands are also factors
watch from 35 sec on
Any one know why the balloon did not pop with water inside?
Hint: Water is good at absorbing heat since it has a higher heat capacity which we will talk about later.
More surface area = faster energy transfer
Material , W/m · °C*
Mercury (l) 8.54
The thermal conductivity of a material can be defined as the rate of heat transfer through a unit thickness of the material per unit area per unit temperature difference.
Water (l) 0.607
Human skin 0.37
Wood (oak) 0.17
Helium (g) 0.152
Soft rubber 0.13
Glass fiber 0.043
Air (g) 0.026
Urethane, rigid foam 0.026
Air also uses convection like the oil inside
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. (waves)
All matter with a temperature greater than absolute zero emits thermal radiation.
When something has minimal molecular movement
Never achieved because heat can always get to the object
Some substances become superconductors at low temperatures
This computer has little or no resistance when operating
It is still unknown why things become superconductors
Even when there is no air or object touching another, radiation still reaches the object preventing it from reaching absolute zero like in space
Also in order to measure that something is at absolute zero would also contribute to the object gaining energy
Measuring the temperature is counterintuitive
No math required...
If Jack Frost is not hot, then he absorbs heat from hot people
"Just leave already"
Blankets and Oven Mitts
Since blankets don't transfer radiation well, energy stays inside to keep you warm
Oven mitts keep the energy out so you don't bun yourself
The number of heat units needed to raise the temperature of a body by one degree.
The molar heat capacity is the heat capacity per unit amount (SI unit: mole) of a pure substance and the specific heat capacity, often simply called specific heat
Items have different heat capacities resulting in a shorter long time to heat up and cool.
Name three examples of conduction.
Name three examples of convection.
Name three examples of radiation.
Practice what you have learned
Did you know that most of the earth's energy comes from the sun through radiation?
It takes an 8 minute journey through space to reach us.
Humans define hot and cold relative to themselves like big and small
Substances can boil at cold temperatures like liquid Nitrogen(-320.44°F)
Substances can also freeze at very high temperatures like steel (2500°F)
As we learned earlier from the Heat of Fusion and Heat of Vaporization lab, when thermal energy is added, the object melts or liquid boils and the inverse is also true.
use different examples
The thermal conductivities of some materials at room temperature
It is the property of a material to conduct heat that varies per substance.
If a substance has low thermal conductivity, then it is a good insulator.
A Few Examples
Types of Friction
resists relative lateral motion of two solid surfaces in contact between non-moving surfaces.
describes the friction between layers of a viscous fluid that are moving relative to each other.
is the force resisting motion between the elements making up a solid material while it undergoes deformation.
The resistance that one surface or object encounters when moving over another.
The kinetic energy is converted to thermal energy
Ex1: A meteor burning up in the atmosphere
Ex2: Starting a fire with a stick
Ex3: Striking a match or lighting a lighter
Watch from 55 sec and mute
When Your Hands Are Cold...
Use friction to warm them up
Law of Conservation of Energy
Like matter, the law of conservation of energy states that the total energy of an isolated system cannot change. Energy can be neither created nor destroyed, but can change form.
No system without an external energy supply can deliver an unlimited amount of energy to its surroundings.
Aerogel's chemical make up:
Si(OCH2CH3)4 (liq.) + 2H2O (liq.) = SiO2 (solid) + 4HOCH2CH3
Thanks For Watching
When you add heat, atoms vibrate faster meaning they need more volume
Its only creepy if you stare too long
Convection In Space
If there is no gravity, then how do denser substances sink?