Enter your Sign-on user name and password.

Forgot password?
  • Follow us on:
Loading video...

Start Learning Now

Our free lessons will get you started (Flash® 10 required).
Get immediate access to our entire library.

Sign up for Educator.com

Features Overview

  • Get on-demand access to our complete library
  • Search and jump to exactly what you need to learn
  • Track your progress
  • Download practice and lesson files
  • *Ask questions and get answers from our community & instructors

Entropy and Second Law of Thermodynamics

  • One-way processes: Some processes will happen only in a certain way: heat flows from hot to cold, not the other way around, and air spreads throughout a room, but never get concentrated in only the left half of the room. Energy conservation is satisfied even if a process goes the wrong way; the fact that it does not mean that there must be another property of the system that defines whether a process occurs. This is entropy.
  • For an irreversible process in a closed system, entropy always increases; in a way, entropy change defines the arrow of time.
  • If an amount of heat Q is added to a system at constant temperature T, the entropy changes by Q/T.
  • The entropy statement of the second law of thermodynamics: The entropy of a closed system never decreases. For an irreversible process the change of entropy is positive; for a reversible process it is zero.
III. Waves

Entropy and Second Law of Thermodynamics

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

AP Physics B