Zeroth Law of Thermodynamics and Temperature Measurement

THERMODYNAMICS DAY 1

THERMODYNAMICS

study of laws that governavailability of energydirection of energy flowconversion of energy how energy transformations relate

to the properties of matter

ENERGY*

Chemical Electrical Solar Nuclear Mechanical

Kinetic Energy Potential Energy

Internal Energy Energy in transit

– Work– Heat

CONCEPT CHECK An iron rod with temperature T1 is connected

to a copper ring with temperature T2 for a long period of time. If we separate the metals, the final temperature of the iron rod is ___.1. less than T12. greater than T13. less than T24. greater than T25. approximately equal to the final temperature of

the copper ring

ZEROTH LAW OF THERMODYNAMICS

“If objects A and B are separately in thermal equilibrium with a third object C, then objects A and B are in thermal equilibrium with each other.”

CONCEPT CHECK

Two bodies are in thermal equilibrium when ___1. both are insulated.2. both have the same volume.3. both have the same temperature.4. both interact with different bodies at

different temperatures.5. one is cold and the other is hot.

THERMAL EQUILIBRIUM

Two objects in thermal equilibrium with each other are at the same temperature.

CONCEPT CHECK

Which of the following statement(s) about temperature is(are) incorrect?1. Temperature is “hotness”.2. Temperature is a measure of heat.3. Temperature is a measure of kinetic

energy.4. Temperature is what a thermometer says.

TEMPERATURE: MACROSCOPIC DEF’N

quantity that tells how warm or cold a substance is with respect to some standard

TEMPERATURE SCALES

SCALE

Freezing point

of water

Boiling point of water

T

Celsius 0 C 100 C 100 CFahrenheit 32 F 212 F 180 F

Kelvin 273 K 373 K 100 K

TEMPERATURE CONVERSION

FTT CF 325

9

329

5 FC TT

TEMPERATURE: MICROSCOPIC DEF’N

related to the kinetic energies of the molecules of the substance

CONCEPT CHECK

A newspaper article about the weather states that “the temperature of a body measures how much heat the body contains.” Is this description correct?

HEAT

energy transfer from one object to another object as a result of a difference in temperature between the two

TEMPERATURE MEASUREMENT

Temperature cannot be directly measured; but many properties of matter that we can measure depend on temperature.

THERMOMETRIC PROPERTIES

physical properties that change with temperature

16

mercury glass thermometer

volume

gas thermometer

pressure

thermistor

resistance

ear thermometer

EM radiationthermocouple

Seebeck effect

QUESTION

Why does a nurse taking your temperature wait for the thermometer reading to stop changing?

CONDITIONS NECESSARY FOR TEMPERATURE MEASUREMENT

In thermal contact – can exchange energy in the form of heat

In thermal equilibrium – has achieved the same temperature

ZEROTH LAW AND TEMPERATURE MEASUREMENT

Choose reference points Construct a scale Mark temperature readings of the reference

points

MERCURY

BODYREFERENCE

QUIZ (1/4 sheet), show solution

You propose a new temperature scale, with temperatures given in °M. You define 0.0 °M to be the normal melting point of Mercury and 100.0 °M to be the normal boiling point of Mercury.A temperature change of 10.0 M°

corresponds to how many C°?What is the normal boiling point of water in

°M?