Absolute Zero

-273.15 0C, 0 KelvinCharles’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 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.

Kelvin Scale

- 273.15 0C is usually rounded to - 273.15 0C

The zero point on the Kelvin Scale is absolute zero

K = 273 + 0CKelvin 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 + by and x are variables

y = temperaturex = volume

m and b are constantsm = slope of the lineb = y intercept

Straight Line Equation

y = mx + bWhen 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 + bWhen b = 0, the line equation is:

y = mx + b

In Charles Law:y = Volumex = Kelvin Temperaturem = 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:StatUp arrow to L1

ClearEnterMove cursor arrow to L2

ClearEnter

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):StatMove cursor to calc82nd 1,2nd2

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?

Volume-Temperature Graph

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Vol

ume

(mL)

Temperature (C) 0 100 – 273