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Notes-Heat Transfer Methods & Phase Changes
3 Methods of Heat Transfer
 Conduction: collisions, heat moves from particle to particle, it allows heat to move through a substance,
ex. Fire on stove goes through pan to heat the water,
ex.
Mainly in the solid state
An insulator stops or delays the movement of heat. Therefore an insulator feels warm.
Examples:
A conductor allows heat to move through it. Therefore it feels cold.
Examples:

Convection: in liquids and gases, this uses a current or a cycle, (hot rises, cools off, sinks, warms,
rises, etc)

Radiation: Dangerous when there is lots of heat energy, radiation is when you “feel” heat
There are 3 STATES OF MATTER: solid, liquid, gas
How does heat make a solid change into a liquid, or a liquid into a gas, etc????
We call these phase changes.
There are 4 Phase Changes, or sometimes called Changes of State

Melting:

Freezing:

Evaporating:

Condensing:

5th Weird one –sublimation-is when a solid becomes a gas by skipping the liquid phase
Examples:Dry Ice
due to the warmth in the room, the dry ice picks up so much heat it goes from
a solid to a gas.
Air Freshener goes from a solid to a gas, it is absorbing energy yet the
temperature doesn’t change
Phase Change Diagram-Very Important --- You will be asked to recreate this!!!!
Notice in the Phase Diagram:
1. A solid can increase in temperature and kinetic energy
2. At 0 degrees Celsius the solid will begin to Melt
3. While Melting, the temperature DOES NOT change, yet the amount of Kinetic Energy is still increasing.
4. When the kinetic energy hits a certain point, a liquid is formed. A liquid can increase in temperature
and kinetic energy until it starts to Evaporate.
5. While evaporating, the temperature DOES NOT change, yet the amount of Kinetic Energy is still
increasing.
6. At a certain point in kinetic energy, a gas is formed and temperature as well as kinetic energy can
increase.
7. Going backwards, a gas can turn into a liquid by loosing energy and temperature, and a liquid can turn
into a solid by loosing energy and temperature.
8. Also, during the phase changes from Gas to Liquid (Condensation) and from a Liquid to a Solid
(Freezing) the temperature DOES NOT change.
When you have a solid, if you put heat energy in, the particles start to move faster until their bonds begin to
break apart to where they can slide past each other. Now that the particles are moving a little faster, you have
a liquid. The point this occurs is called Melting Point. Once melted, there are no forces holding the particles in
the solid state. As the energy continues to increase, the motion increases and therefore the temperature
increases. Some particles begin to break free from other particles. This point is called the Boiling Point.

Heat of Fusion: amount of energy needed to melt or freeze a gram of the substance. The symbol is L.
The value for this for water is 80 cal/g

Heat of Fusion: amount of energy needed to evaporate or condense a gram of the substance.
The symbol is L.
The value for this for water is 240 cal/g.
Q=mL
Example 1:
How many calories of heat are necessary to melt 20 grams of ice at its freezing point?
Example 2:
How much heat is needed to vaporize 250g of water at its boiling point?
Example 3:
Heat is applied to 100 g of ice at 0 degrees Celsius until the ice melts and the temperature of the resulting
water rises to 20 degrees Celsius. How much heat is absorbed?