1. Heat Transfers 1

2. Then you have witnessed heat, but how would you define it??
What is Heat?
Ever feel the warmth from a fire?
Touch a hot iron and burn yourself?
Watch water boil on the stove?
Then you have witnessed heat, but how would you define it??

3. What is Heat?
Heat is the movement of energy from a warm object to a cool object.
Energy passes through atoms
Temperature is a measure of how much energy is in an object.

4. How Does Heat Move? Heat moves through objects in three main ways:
1. Conduction
2. Convection
3. Radiation

5. Methods of Heat Transfer
Conduction — When the two objects actually touch. This is the best method.
Example:
If you hold an ice cube in your hand the ice cube melts.
The heat energy passes from your hand to the ice.

6. Methods of Heat Transfer
Convection — Through a circulation of fluid.
Example: Air circulating through your room, water boiling in a pot, and lava lamps are examples of convection

7. Methods of Heat Transfer
Radiation — Energy leaving in the form of an electromagnetic wave (such as light). Radiation is the slowest form, but it is impossible to stop.
When heat energy does not need to travel through particles it is known as radiation.
Example: The heat from the
sun travels by radiation

8. Conductors and Insulators
Conductors — Materials that allow heat to quickly pass throughout the material (such as metals and glass).
Insulators — Materials that do not allow heat to quickly pass throughout a material (such as wood, foam or plastic).
This mainly deals with the movement of electrons.
Metals have a “sea of electrons” that allows for quick heat transfer.

9. Thermos
A thermos is a container that is capable of keeping hot items hot and cold items cold.
You probably had a cheap one when you were younger in your lunchbox.
You can buy better ones that keep beverages hot or cold much longer.
A thermos (or a cooler or even an insulated cup) works by preventing transfers of heat!

10. How a Thermos Works You have a jar inside a jar.
Good ones have a vacuum (nothing) in between the jars.
Cheap ones have Styrofoam in between.
Outer jar
Vacuum or
little air
The problem arises in
keeping them apart!
Inner jar
You need to have points
to support, and conduction
occurs here. 10

11. Why Metals Feel Cool to the Touch at Room Temperature
Room temperature is cooler than human body temperature.
Heat is ONLY noticed when there is a transfer!
Metals quickly conduct heat from your body throughout the metal (since it is taking heat, it feels cold).
Wood and plastic don’t conduct heat quickly, so not as much is taken from your skin.
Good insulators normally have a lot of space for air, because gases don’t conduct as well as solids.

12. Convection and Radiation
The sun radiates heat in the form of light toward the planet.
This heats the surface, which conducts heat to the air it touches.
The hot air expands and begins to rise.
Cooler air fills the void the hot air left.
The air begins to circulate.
The circulation is convection; light (energy) is radiation.
Earth

13. Fluid Movement
Cooler, more dense, fluids sink through warmer, less dense fluids.
In effect, warmer liquids and gases rise up.
Cooler liquids and gases sink.

14. Why is it windy at the seaside?

15. Radiation
How does heat energy get from the Sun to the Earth?
There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. ?
RADIATION

16. Radiant Energy
Radiation can be visible light, but can also be a large spectrum of objects such as …