13-3 thermal equilibrium and the zeroth law of thermodynamics

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 3rd 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.

• DL= aLo DTc

• L= Lo (1 + aDT) …see page 388 for chart

• See Example 13-3 13-6 on page 389

• …For volume expansion, DV= bVo DTc

• See Example 13-7 p390

13-5 Anomalous Behavior of Water

• If water, at 00 C is heated it decreases in volume until it reaches 40 C

• See page 391 graph

13-6 Thermal Stresses

• DL= aLo DTc

• DL= (1/ )(E F/A) Lo

• aLo DTc = (1/ )(E F/A) Lo

• So…F= aEA DTc

• See Example 13-8

13-7 The Gas Laws and Absolute Temperature

• PV/T= (P2 V2 /T2) …The combined gas law…

• PV= P2 V2 Boyle’s Law

• P/T= (P2 /T2) Gay-Lussac’s Law

• V/T= V2 /T2 Charle’s Law• Use Kelvin temperature for all kinetic/gas

problems

Homework

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