1. heat                      7. conduction
                                                            2. temperature          8. convection
                                                            3. energy                  9. radiation
                                                            4. thermal energy    10. calorimeter
                                                            5. specific heat        11. heat of vaporization
                                                            6. insulation             12. heat of fusion
 
 

HEAT- the total kinetic energy (internal energy) possessed by a substance due to the motion of its molecules. This energy depends on the mass and the temperature of the substance.

Example:

same X has more total kinetic energy because
temperature it has greater mass (more total molecules in motion).
 
 
 
 
 

NOTE: When a substance is heated, its molecules vibrate more quickly and move further apart causing it to expand.

OOOO       O O O O       O     O     O     O
OOOO       O O O O       O     O     O     O Expansion occurs
OOOO       O O O O       O     O     O     O

----------increase in heat------------->
 
 

In contrast, when matter is cooled, the molecules slow down and move closer together; as a result, the volume of the substance decreases.

NOTE: Heat is measured in calories or joules (J).
One calorie= 4.18 joules
 
 

THERMAL ENERGY - the total energy of all the particles in an object.
 
 
 

TEMPERATURE - is a measure of the average kinetic energy of the particles in a material.

Temperature is expressed in degrees, either Celsius (C) or Fahrenheit (F).

Celsius (C) Fahrenheit (F)

Boiling point of water 100 degrees C or 212 degreesF

Freezing point of water 0 degrees C or 32 degrees F

NOTE: Temperature shows the tendency of a material to gain or lose heat. When you put a thermometer in a glass of ice water, the column of mercury drops (the thermometer lost heat to the ice water). If you put the thermometer in boiling water, the column of mercury rises (the thermometer gained heat from the boiling water).

Heat flows from regions of higher temperature to regions of lower temperature.

REVIEW: Remember heat and temperature are not the same.
Temperature is average kinetic energy.
Heat is total kinetic energy (it depends on both mass & temperature).

If two different quantities (different masses) of the same substance have the same total energy, it must be true that the temperature of the larger quantity is lower (cooler).

SPECIFIC HEAT (Cp) - is the ability of a material to absorb heat. It is measured using the units joule per gram Celsius degree (J/g^oC).

Specific heat of :
a) water = 4.18 J/g^oC
b) copper = 0.38 J/^ogC

Measuring Heat - changes in the heat energy of a material can be measured.

H
heat absorbed = (t2 - t1) X m X Cp
or change in mass specific heat
released temperature of the substance
 
 
 

Example problem: Ten grams of water are heated from 50C to 200C.
How much heat energy is absorbed by the water?

H = (t2 - t1) x m x Cp
= (200C - 50C) x 10g x 4.18 J/gC
= 150C x 10g x 4.18 J/gC
= 627J

Solve the problem: A 40 gram piece of copper is cooled from 800C to 700C. How much heat is lost by the copper?

FLUID - a substance that flows (liquids & gases).

CALORIMETER - an instrument used to measure changes in thermal energy.

HEAT OF FUSION - the energy needed to change from the solid to the liquid state.

HEAT OF VAPORIZATION - the energy needed to change from the liquid to the gaseous state.

HEAT TRANSFER (movement)

a) Conduction: movement of heat from particle to particle. It occurs when tow objects at different temperatures are in direct contact. Example: heating an iron pot on a stove.

b) Convection: movement of heat with particles within liquids and gases. Example: the central heating system of some homes.

NOTE: Winds and ocean currents are convection currents that transfer heat on Earth.

c) Radiation: transfer of heat through space without particle movement. It does not require matter. Example: warmth from the sun.

INSULATION - reduces the flow of heat by conduction, convection, and radiation. It does not allow heat to move easily.

Examples: picnic coolers, thermos bottles, weather stripping, double paned windows, fiberglass.
 

NOTE: Evaporation is a cooling process. During evaporation a liquid absorbs heat, heat is removed from the surroundings. Examples: perspiration, air conditioners.