Download Temperature and Thermal Energy Part One

In this lesson, we
will discuss the
following:
Temperature and
Thermal Energy:
Part 1
Physics
Temperature
Absolute Zero
Thermal Energy
Classroom Ambush: Define
Temperature
Temperature
On the
macroscopic
scale,
temperature is
a measure of
how warm a
substance is.
If something is macroscopic, it can
be seen with the naked eye.
Temperature
• Molecules and atoms can move in three
different ways. The three kinds of particle
motion are as follows:
– Translational motion is motion in straight lines.
– Rotational motion is the motion of a particle as it
rotates on its own axis.
– Vibrational motion is the shaking or vibrating of
atoms or molecules.
Translational
motion is
motion in
straight lines.
Temperature1
Rotational
motion is the
rotation of a
particle about
its own axis.
Temperature1
Vibrational
motion is the
shaking or
vibrating of
molecules or
atoms.
Temperature1
Temperature
On the
microscopic and
submicroscopic
scales,
temperature is
defined as the
average
translational
kinetic energy per
particle (atom or
molecule) of a
substance.
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Temperature
In other words,
temperature is
basically a
measure of how
fast molecules
or atoms are
moving in
straight lines.
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Temperature
• Temperature is a “per particle” property. In
other words, you can measure the
temperature of an individual atom or
molecule.
• In addition, for constant conditions, the
temperature of a substance is independent of
number of molecules or atoms. A substance
can have a very high temperature even if it is
made of very few molecules.
Abbreviation for Temperature
We will abbreviate temperature as T.
Temperature Scales
• The two temperature scales we will see in our
class are the Celsius scale and the Kelvin scale.
– The Celsius scale has 00 Celsius at the freezing point of
fresh water and has 1000 Celsius at the boiling point of
fresh water. The Celsius scale is sometimes called the
Centigrade scale.
– The Kelvin scale has 0 Kelvin (not degrees in Kelvin
scale) at absolute zero, and for this reason, the Kelvin
scale has no negative temperatures. The Kelvin scale
is also called the Absolute scale. On the Kelvin scale,
the freezing point of fresh water is 273 K, and the
boiling point of fresh water is 373 K.
Temperature Scales
When in doubt, use the Kelvin scale!
SI Unit for Temperature
The proper SI Unit for Temperature is the
Kelvin (K). DO NOT USE the word “degrees”
when expressing temperature in Kelvin.
Temperature is a Scalar Quantity
Temperature is a scalar quantity. In other
words, temperature has no direction.
Absolute Zero
• Temperature has NO upper limit. In other
words, temperature can theoretically increase
infinitely.
• However, temperature DOES have a lower
limit. This lower limit is called absolute zero.
• In fact, temperature can never quite actually
reach absolute zero, it can just approach it.
• When a substance
has reached
absolute zero, all
of its particles
(molecules and
atoms) have lost
all available
energy.
• A substance can
never get any
colder than
absolute zero. In
fact, a substance
can’t quite get to
absolute zero.
Absolute Zero
• On the
Fahrenheit scale,
absolute zero is
−459.670 F.
• On the Celsius
scale, absolute
zero is -2730 C.
• On the Kelvin
scale, absolute
zero is 0 K.
Absolute Zero
Thermal Energy
• Thermal energy is defined as the total energy
of all of the particles that make up a
substance.
• The more particles a substance has, the higher
its thermal energy.
Why Doesn’t a
Sparkler Burn You?
• A sparkler emits sparks which are very hot
(about 20000 C).
• But, a sparkler only emits a few sparks.
• Because only a few sparks are emitted by a
sparkler, the thermal energy that a sparkler
can transmit to your hand is quite small.
• Your hand does not get burned because very
little thermal energy is transferred from the
sparks to your hand.
Abbreviation for Thermal Energy
We will abbreviate thermal energy as
Eth
.
Acceptable Units for Thermal Energy
• The SI unit for all energy is the Joule, but the
calorie, and the Calorie are also acceptable
units.
4,180 J  1,000calories  1Calorie
Thermal Energy is a Scalar Quantity
Thermal energy is a scalar quantity (like all
other forms of energy). Thermal energy has
no direction.