Science Ideas

We can encounter heat transfer in our daily life. This is what we usually observe when we boil water in a pot.

Here are some inputs that defines Heat Transfer:

• Heat always moves from a warmer place to a cooler place.
• Hot objects in a cooler room will cool to room temperature.  
• Cold objects in a warmer room will heat up to room temperature.

There are three methods of Heat Transfer:  Conduction, Convection and Radiation    

Conduction  
When you heat a metal strip at one end, the heat travels to the other end. As you heat the metal, the particles vibrate these vibrations make the adjacent particles vibrate, and so on, and so on, the vibrations are passed along the metal and so is the heat. We call this Conduction .

Metals are different.
The other electrons of metal atoms drift, and are free to move. When the metal is heated, 'this sea of elections' gain kinetic energy and transfer it throught the metal. Insulators such as wood, and plastic do not have this 'sea of electrons' which is why do not conduct heat as well as metals.


Why does metal feel colder than wood, if they are both at the same temperature?
Metal is a conductor, wood is an insulator. Metal conducts heat away from the hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal. 


Convection 
What happens to the particles in a liquid or a gas when you heat them? The particles spread out and become less dense. This effects the fluid movement. 

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

Radiation

How does heat get energy from the Sun to the Earth? There are no particles between the Sun the the Earth so it cannot travel by conduction or by convection. It is by radiation. Radiation travels in a straight line, can travel through a vacuum, requires particles to travel, and travels at speed of light.




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