1. heat work and first law

# 1. heat work and first law - Work… w What are the types...

This preview shows pages 1–2. Sign up to view the full content.

Thermodynamics 1. Heat, Work, and the First Law of Thermodynamics Reading assignment in the textbook… Pressure, temperature, and the ideal gas: Sections 1.1, 1.2 (This material will not be covered in class, but you should know it!) Heat and work: Sections 2.1, 2.2, 2.3, 2.4 (Study the figures carefully!) ---------------------------------------------------------------------------------------------------------- The system and the surroundings. There are 3 types of thermodynamic system. See fig. 2.1 Ways to transfer energy through the boundary of the system… Heat (q) . . transfer of energy that makes use of random molecular motion in the surroundings. Work (w) . . transfer of energy that makes use of organized molecular motion in the surroundings. How do you know if it’s q or w? Always look at the surroundings! See figs. 2.3 and 2.4 Heat… q The sign convention. When is q positive? q is a path function. What are state functions and path functions? Some examples: drive to Houston, or climb a mountain…

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Work… w What are the types of work? See table 2.1 Now for mechanical work… in particular, work involved in changing the size (volume) of the system. First. . comments about pressure. What are the units? Pascal, bar, atm., standard pressure. Expansion of a gas in a piston-cylinder machine Derive: ext dw P dV = -and 2 1 ( ) V ext V w P V dV = -Sign of w: negative Compression of gas in piston-cylinder machine: 2 1 ( ) V ext V w P V dV = -Sign of w: positive Note: w depends on P ext , NOT P int (see just below equation 2.6) Plot these processes on a diagram: Plot P ext vs. V Sign of the area; sign of w w is a path function (like q) The first law of thermodynamics Law of conservation of energy applied to q and w Introduce a new function: U, the internal energy Here is the first law: 2 1 U U U q w ∆ =-= + Also. . U is a state function The sum of two path functions gives a state function!...
View Full Document

## This note was uploaded on 05/18/2010 for the course CH 353 taught by Professor Wyatt during the Spring '10 term at University of Texas-Tyler.

### Page1 / 2

1. heat work and first law - Work… w What are the types...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online