Thermal properties of matter

Temperature measurement

• Thermometric properties = Properties changing with temperature– Color– Volume– Length– Electric resistance

• thermistor

– Electric voltage• thermocouple

Reading Assignment 17.1

You put a thermometer in a pot of hot water and record the reading. What temperature have you recorded?

A. The temperature of the water

B. The temperature of the thermometer

C. An equal average of the temperature of the water and thermometer

D. An average between water and thermometer, shifted more toward water

E. An average between water and thermometer, shifted more toward the thermometer

Celsius scale

Ice water Boiling water

0°C

100°C

0°C

Thermal equilibrium

Fahrenheit scale

Salt/ water/ ice mixture

Arm pit

0°F= -17.8°C

96°F

0°C

Recalibration:32 F = 0 C212 F = 100 C

Thermodynamic temperature

pressure versus temperature for a gas in closed volume

-50

-30

-10

10

30

50

70

90

110

130

-300 -200 -100 0 100

temperature (C)

pre

ssu

re (

kPa

) -273.15 C

P, T

T

Temperature transformations

Umm Weather Station

Maximum temperature in March: 50.3 F

Minimum temperature in March: -13.9 F

-20

-10

0

10

20

30

40

50

60

3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31

-20

-10

0

10

20

30

40

50

60

dew point

temperature

Express those temperatures in Celsius and Kelvin.

Express the temperature difference in C, F, and K.

A 30-cm square rubber sheet with handle:

What is the force of air pressure pushing it to the table?

The density of copper is 8.2 g/cm3.

Find

A. The number of atoms in one cubic centimeter of copper.

B. The average distance between the atoms.

Repeat for silver (density 10.49 g/cm3).

Linear thermal expansion

T0, L0

L

T, L

oL T T

0L L 0 0L L T T

1611 10 osteel C

1612 10 oconcrete C

See table 12.2

Pontchartrain Causeway

Lake Pontchartrain is a large shallow brackish lake bordering New Orleans to the north. A 23-mile causeway bridge is leading over the lake.

The temperatures in winter drop to about 35F, while in summer the surface temperature of the bridge easily surpasses 120F.

Estimate the length difference of this concrete causeway between winter and summer.

Volume expansion

0 0V V T T

0 0 0L L L T T

Relation between volume expansion coefficient and linear expansion coefficient?

3

Causes of thermal expansion?

x

Potential energy of bond

Distance between two particles

Spring-like bonds

Equilibrium distance

Realistic bonds

Equilibrium distance

Asymmetric binding energyresults in thermal expansion of solids

Behavior of gases

Consider a cylinder filled with air. A piston is slowly being pushed to the left.

Assume, the gas is in thermal equilibrium with its surroundings.

When the volume of gas will become smaller, will the pressure1 increase?2 decrease?

3 stay the same?

290 K 290 K pV constBoyle’s Law

Isothermal process

Behavior of gases

Consider the same cylinder.The piston is free to move without friction (p=const).

A flame is slowly heating the air inside.When the temperature of the air increases, will the volume

1 increase?2 decrease?

3 stay the same?

P=1atmP=1atm .

Vconst

T

Charles’ Law

Isobaric process

Behavior of gases

Consider the same cylinder.The piston is fixed (V=const).

A flame is slowly heating the air inside.When the temperature of the air increases, will the pressure

1 increase?2 decrease?

3 stay the same?

pconst

T

Gay-Lussac’s Law

Isochoric process

Ideal gas law

pV nRT

8.314J

Rmol K

How many kg of air would we find in the auditorium at this time?

D=1.23 kg/m3

Phase diagrams of the ideal gas0

.00

.51

.01

.52

.0

0

50

10

0

15

0

molar volume (L/mol)

pre

ssu

re (

atm

)

200 K

500 K

800 K

0.0

0.5

1.0

1.5

2.0

0 200 400 600 800temperature (K)

pre

ssu

re (

atm

)

1000L/mol100L/mol50L/mol

0

50

100

150

0 200 400 600 800temperature (k)

mo

lar

volu

me

(L

/mo

l)

0.5 atm1 atm1.5 atm