Absolute Zero
-273.15 0C, 0 Kelvin
Charles’s Law
Absolute Zero
 Theoretically, absolute zero is the
lowest temperature that can be
reached.
 Absolute zero has never been reached.
 Temperatures within a millionth of a
degree above -273.15 0 C have been
achieved!
Lord Kelvin
 The Kelvin scale is named after Lord
Kelvin and his scale starts at 0 degrees
Kelvin, which is called absolute zero.
 The Kelvin Scale measures the coldest
temperature there can be.
Lord Kelvin
1824 - 1907
 Lord Kelvin said there was no upper limit of
how hot things can get, but there was a limit
as to how cold things can get.
 Kelvin developed the idea of Absolute Zero:
- 273.15 degrees Celsius!
 At this temperature, no heat energy remains
in a substance, the average kinetic energy is
zero and all molecular motion ceases.
Kelvin Scale
 - 273.15 0C is usually rounded to - 273.15 0C
 The zero point on the Kelvin Scale is
absolute zero
 K = 273 + 0C
 Kelvin is the SI unit of temperature
Charles’s Law
 V1/T1 = V2/T2
 By measuring and graphing the volume
and temperature of a gas and
extrapolating to 0 volume, absolute
zero can be determined.
Straight Line Equation
 y = mx + b
y and x are variables
y = temperature
x = volume
 m and b are constants
m = slope of the line
b = y intercept
Straight Line Equation
 y = mx + b
When b = 0, the line equation is:
y = mx + b
This is a direct proportion -- the special
case of a straight line having a y-intercept
= to zero.
Straight Line Equation
 y = mx + b
 When b = 0, the line equation is:
y = mx + b
In Charles Law:
y = Volume
x = Kelvin Temperature
m = k2 proportionality constant for a particular
pressure
Charles’s Law
 Charles’s Law states:
At constant pressure, the volume of a fixed
amount of gas is directly proportional to its
absolute temperature.
K2 = V/T
V1/T1 = K2 = V2/T2
V1/T1 = V2/T2
Linear Regression
 Linear regression analyzes the relationship
between two variables, X and Y.
 For each subject (or experimental unit), you
know both X and Y and you want to find the
best straight line through the data.
 In some situations (like finding absolute
zero), the slope and/or intercept have a
scientific meaning.
Linear Regression
 The goal of linear regression is to adjust the
values of slope and intercept to find the line
that best predicts Y from X.
 The slope quantifies the steepness of the
line. It equals the change in Y for each unit
change in X. It is expressed in the units of
the Y-axis divided by the units of the X-axis.
 The Y intercept is the Y value of the line
when X equals zero. It defines the elevation
of the line.
TI-83 Linear Regression
 Clear Previous Data:
Stat
Up arrow to L1
Clear
Enter
Move cursor arrow to L2
Clear
Enter
TI-83 Linear Regression
 Enter x values:
<
Enter all x values in L1
Enter after each value
TI-83 Linear Regression
 Enter y values:
>
Enter all y values in L2
Enter after each value
TI-83 Linear Regression
 Find slope (b), Intercept (a), and correlation
coefficient (r):
 Stat
 Move cursor to calc
8
 2nd
1
,
 2nd
2
Linear Regression
 If the slope is positive, Y increases as X
increases.
 If the slope is negative, Y decreases as
X increases.
 The Y intercept is the Y value of the
line when X equals zero. It defines the
elevation of the line.
Linear Regression
 Is the slope positive or negative for
determining absolute zero?
30
25
20
15
10
5
– 273
0
Temperature (C)
100
Volume (mL)
Volume-Temperature Graph