Thermal energy is related to the kinetic energy and potential energy of molecules. The temperature of an object is a measure of the average kinetic energy of its molecules - the higher the temperature, the faster molecules move and the more kinetic energy they have. When temperature increases, molecules speed up and objects expand; when temperature decreases, molecules slow down and objects contract. Thermometers measure temperature by using the expansion and contraction of liquid in a tube in response to temperature changes. Common temperature scales are Celsius, Fahrenheit, and Kelvin.

1. THERMAL
ENERGY
Chapter 21, Section 1
Temperature andThermal Energy

2. Kinetic
Energy and
Temperature
Kinetic Energy is energy of motion.
How hot or cold something feels is related to its
temperature.
Temperature is a measure of the average value of the
kinetic energy of the molecules in random motion.
The more kinetic energy molecules have, the higher
the temperature.
Molecules have more kinetic energy when they are
moving faster.

3. Thermal
Expansion
When the temperature of an object is increased, its
molecules speed up and tend to move farther apart.
This causes the object to expand.
When the temperature of an object is decreased, its
molecules slow down and move closer together. This
causes the object to shrink or contract.
Almost all substances expand when they are heated
and contract when they are cooled.
The amount of expansion or contraction depends on
the type of material and the change in temperature.

4. Measuring
Temperature
The temperature of an object depends on…the average
kinetic energy of all the molecules in an object.
The practical way to measure temperature is with a
…thermometer because they use the expansion and
contraction of materials to measure temperature.
A thermometer works when the temperature of the
liquid increases, it expands so that the height of the
liquid in the tube depends on the temperature.

5. Temperatur
e Scales
The three temperature scales are Celsius, Fahrenheit
and Kelvin.
Celsius: freezing point is 0, boiling point is 100
Fahrenheit: freezing point is 32, boiling point is 212
Kelvin: absolute zero is lowest temperature an object
can have.
Know formulas.

6. Thermal
Energy
Potential Energy is energy that the molecules have
that can be converted into kinetic energy.
Thermal energy is the sum of the kinetic energy and
potential energy of all the molecules in an object.
As molecules get closer together or farther apart, their
potential energy changes.