Absolute Zero

1. Absolute Zero -273.15 0C, 0Kelvin 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 -273.15 0 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 Kelvin1824 - 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.

5. 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

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: y = mx + b 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: y = mx + b 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 • Clear • Enter

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 • , • 2nd • 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. 30 25 20 Volume (mL) 15 10 5 0 100 Temperature (C) Volume-Temperature Graph – 273