1. -273.15 0C, 0 Kelvin Charles’s Law
Absolute Zero
C, 0 Kelvin
Charles’s Law

2. 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 C have been achieved!

3. 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.

4. Lord Kelvin
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: degrees Celsius!
At this temperature, no heat energy remains in a substance, the average kinetic energy is zero and all molecular motion ceases.

5. Kelvin Scale - 273.15 0C is usually rounded to - 273.15 0C
The zero point on the Kelvin Scale is absolute zero
K = C
Kelvin is the SI unit of temperature

6. 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.

7. 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

8. Straight Line Equation
y = mx + b
When b = 0, the line equation is:
This is a direct proportion -- the special case of a straight line having a y-intercept = to zero.

9. Straight Line Equation
y = mx + b
When b = 0, the line equation is:
In Charles Law:
y = Volume
x = Kelvin Temperature
m = k2 proportionality constant for a particular pressure

10. 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

11. 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.

12. 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.

13. TI-83 Linear Regression Clear Previous Data: Stat Up arrow to L1 Clear
Enter
Move cursor arrow to L2

14. TI-83 Linear Regression Enter x values: < Enter all x values in L1
Enter after each value

15. TI-83 Linear Regression Enter y values: > Enter all y values in L2
Enter after each value

16. TI-83 Linear Regression
Find slope (b), Intercept (a), and correlation coefficient (r):
Stat
Move cursor to calc 8
2nd 1 , 2

17. 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.

18. Linear Regression
Is the slope positive or negative for determining absolute zero?

19. Volume-Temperature Graph5 10 15 20 25 30
Volume (mL)
Temperature (C)
100
– 273