[Under Construction]



Heat Transfer


    1.    Describe how heat energy causes molecules to move.

    2.     List examples of heat energy transfer by conduction, convection, and radiation.



Heat energy is created due to the internal motion of molecules in a substance.     Heat can more correctly be explained as the amount of kinetic energy in a substance.  Therefore, the amount of heat in a substance depends on the mass of the object.  Heat transfer is defined as the movement of heat from a warmer substance to a cooler one.  This is technically known as moving down a temperature gradient.  There are three types of heat transfer.

(blueox.uoregon.edu/~courses/dlivelyb/ ph161/globwarm_an.gif)


Transferred by direct contact of molecules
Molecules in hot substances move fast
Collide with cooler, slower molecules and transfer energy  

conduction of heat through a solid(www.gcse.com/energy/images/ conduction.gif)

        Conductors transfer heat well (metals: silver, copper, aluminum, iron)

        Insulators bad conductors of heat (nonmetals:  glass, wood, rubber, & plastics)


Liquids & gases
The molecules in heated gas or liquid move farther apart and become less dense.
The less dense gas of liquid rises
Created a circular current  

convection in heated water



(www.bluffton.edu/~bergerd/NSC_111/ images/waterconvect.gif)









Heat transferred through empty space via infrared radiation

(www.min.uc.edu/nuclear/ ibt/ht2.jpg)

Measuring Heat

Can measure temperature not heat
Unit is the calorie (cal) or joule (J)
1cal = 4.19J
a cal is the amount of heat needed to raise 1g of water 1 degree

The specific heat   of a substance is the amount of heat (cal) needed to raise a substance 1oC .

Can be used to calculate the amount of heat gained or lost by a substance  

measured using a bomb calorimeter

Is the ability of a substance to absorb heat

High specific heat slow to heat up and slow to cool down (& visa versa)  
Can be measured using a calorimeter
Mass DT Specific heat  


Heat PE can be stored in the bonds of fuels and food









Last modified: December 02, 2003