# 13-3 Thermal Equilibrium and the Zeroth Law of Thermodynamics

Mechanics

Oct 27, 2013 (4 years and 6 months ago)

92 views

13
-
3 Thermal Equilibrium and the
Zeroth

Law of Thermodynamics

Two objects in contact, at different temperatures,
will have heat energy travel in both directions, but
mostly, ‘downhill’ to the cooler object until they
reach thermal equilibrium.

The
zeroth

law of thermodynamics
states that if
two objects are in thermal equilibrium with a 3
rd

system, then they are in equilibrium with each other.

13
-
4 Thermal Expansion

Most substances expand when they are
heated and contract when they are cooled.

D
L=
a
L
o

D
T
c

L= L
o

(1 +
a
D
T
) …see page 388 for chart

See Example 13
-
3

13
-
6 on page 389

…For volume expansion,
D
V
=
b
V
o

D
T
c

See Example 13
-
7 p390

13
-
5 Anomalous Behavior of Water

If water, at 0
0

C is heated it decreases in
volume until it reaches 4
0

C

See page 391 graph

13
-
6 Thermal Stresses

D
L=
a
L
o

D
T
c

D
L=
(1/E)(
F/A) L
o

a
L
o

D
T
c

=

(1/E)(
F/A) L
o

So…F=

a
EA

D
T
c

See Example 13
-
8

13
-
7 The Gas Laws and Absolute
Temperature

PV/T= (P
2

V
2
/T
2
) …The combined gas law…

PV= P
2

V
2

Boyle’s Law

P/T= (P
2
/T
2
) Gay
-
Lussac’s Law

V/T= V
2
/T
2

Charle’s

Law

Use Kelvin temperature for all kinetic/gas
problems

Homework

P413
-
414 pr#9
-
13,24
-
25,28
-
30 due Friday BOP