This document discusses key concepts relating to heat, temperature, and thermal energy. It defines heat as the transfer of energy due to a temperature difference, and temperature as a measure of the average kinetic energy of particles in a substance. It also explains different temperature scales, units of heat and thermal energy, heat transfer processes, and the laws of thermodynamics. Phase changes of matter are determined by temperature, with energy absorbed or released during changes between solid, liquid, and gas states.

1. ISNS 3371 - Phenomena of Nature
Heat and Temperature
Heat: The amount of energy transferred from one body to
another by virtue of a temperature difference between
them.
Heat is not the energy content of a body although it is
frequently used that way. The proper term is thermal
energy.
Unit of heat is: Joule
Temperature: A measure of the average kinetic energy of
the molecules of a substance.
That property of a body of matter that gives rise to
sensations of hot and cold.

2. ISNS 3371 - Phenomena of Nature
Temperature and Thermal Energy
Why does water burn your skin so much quicker than air?
Why is falling into a 32º F lake more dangerous than standing outside
naked on a 32º F?
Temperature - measure of the
average kinetic energy of the
particles in a substance -
particles in box on right have
higher temperature - higher
velocity = more KE = higher
temperature
Both boxes have same
temperature - particles have
same average velocity/KE -
box on right has more thermal
energy - energy contained in
a substance - more particles

3. ISNS 3371 - Phenomena of Nature
Temperature is a measure of the average kinetic energy of the particles in a
substance. This diagram compares three common temperature scales. The
Fahrenheit scale is used in the United States, but nearly all other countries use the
Celsius scale. Scientists prefer the Kelvin scale because O K represents absolute
zero, the coldest possible temperature.

4. ISNS 3371 - Phenomena of Nature
TEMPERATURE SCALES
WATER
__________________________
ABSOLUTE ZERO FREEZING POINT BOILING POINT
_________________________________________________
FAHRENHEIT -459° 32° 212°
CELSIUS -273° 0° 100°
KELVIN (ABSOLUTE) 0° 273° 373°
CONVERSIONS:
CELSIUS TO FAHRENHEIT
F = 9/5C + 32
FAHRENHEIT TO CELSIUS
C = 5/9 x (F - 32)
CELSIUS TO KELVIN
K = C + 273.

5. ISNS 3371 - Phenomena of Nature
Thermal Energy
Thermal Energy: Total of all energies, kinetic plus potential, internal
to a substance.
Quantity of Heat: Calorie or Joule
1 calorie = Amount of thermal energy required to change
the temperature of 1 gram of water 1°C.
1 joule = 0.239 calories (1 Calorie = 4.187 joules)
1 kilocalorie = 1,000 calories (usually spelled with a capital C)

6. ISNS 3371 - Phenomena of Nature
Specific Heat Capacity, c: Thermal inertia
Specific Heat Capacity is the quantity of heat required to change the
temperature of 1 gram of a substance by 1°C.
If Q units of of thermal energy added to 1 gram a substance produce a
temperature change of ∆T,
Q = c x ∆T
Specific heat , c, of a substance is the heat capacity per unit mass.
For m grams of a substance,
Q = cm ∆T
Water has high specific heat capacity - used as a cooling fluid.
Specific heat capacity of water is 1calorie per gram-deg. C.

7. ISNS 3371 - Phenomena of Nature
Heat Transfer Processes
Conduction – transfer of heat from a region of higher
temperature to a region of lower temperature by
increased kinetic energy moving from molecule to
molecule through collisions between molecules.
Occurs in solids.
Convection – transfer of heat from a region of higher
temperature to a region of lower temperature by the
flow of higher energy molecules. Occurs in gases
and liquids.
Radiation – transfer of heat by emission and absorption of
radiant energy (energy that can travel through
space as electromagnetic radiation, like visible
light).

8. ISNS 3371 - Phenomena of Nature
The Laws of Thermodynamics
First Law:
Whenever heat flows in or out of a system, the gain or loss
of thermal energy equals the amount of heat transferred.
Second Law:
Heat never spontaneously flows from a cold substance to a
hot substance.
Third law:
No system can reach absolute zero.

9. ISNS 3371 - Phenomena of Nature
The state or phase of matter is
determined by its temperature.
Consider water:
Below 32º F - ice - relatively low
KE - each molecule tightly bound
to it neighbors - solid
At 32º F molecules have enough
energy to break solid bonds of ice
- remain together but move
relatively freely - liquid
At 212º F water boils and turns to
gas - molecules break free of all
bonds with neighbors - move
independently of other molecules
- gas

10. ISNS 3371 - Phenomena of Nature
Phase/State Changes
Melting - when a solid changes to a liquid
Evaporation - when a liquid changes to a gas
Sublimation - when a solid changes directly to a gas
Condensation - when a gas changes to a liquid
Freezing - when a liquid changes to a solid
Energy is
absorbed
Energy is
released
Heat transfer always occurs whenever a substance changes phase