C6F2009 - Chapter 6 Thermochemistry: Energy Flow and...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
© CHEM 1331 Prof. Geanangel, Chapter 6 Dept. of Chemistry, University of Houston 1 Chapter 6 Thermochemistry: Energy Flow and Chemical Change 6.1 Forms of Energy and Their Interconversion 6.2 Enthalpy: Heats of Reaction and Chemical Change 6.3 Calorimetry: Laboratory Measurement of Heats of Reaction 6.4 Stoichiometry of Thermochemical Equations 6.5 Hess’s Law of Heat Summation 6.6 Standard Heats of Reaction ( ! H 0 rxn ) © CHEM 1331 Prof. Geanangel, Chapter 6 Dept. of Chemistry, University of Houston PE of a weight raised above the ground is converted to KE as it falls. As weight hits the ground, it transfers some KE to the soil, causing particles to move, doing work . Also, some of the transferred KE appears as heat . PE in chemical bonds of foods/fuels is converted to KE giving the ability to do work and generate heat. Whenever energy is transferred from one object to another, it appears as work , w , and/or as heat , q . Forms of Energy and Their Interconversion 2 An object has potential energy (PE) by virtue of its position and kinetic energy (KE) due to its motion .
Background image of page 1

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

View Full DocumentRight Arrow Icon
© CHEM 1331 Prof. Geanangel, Chapter 6 Dept. of Chemistry, University of Houston Distinction between a system and its surroundings ! E = E final – E initial = E products – E reactants As a chemical system changes from reactants to products , internal energy of the system changes. Define ! E: pick a system ; that part of the universe whose change is to be measured. The sum of the KE and PE of all the particles in the system is its internal energy , E (or U). 3 ! E, Energy flows to or from a system The energy change, ! E, appears as heat and/or work: ! E = q + w © CHEM 1331 Prof. Geanangel, Chapter 6 Dept. of Chemistry, University of Houston 1. By losing some energy to the surroundings: 2. By gaining some energy from the surroundings: A reacting chemical system can change its internal energy in two ways : 4 ! E = E final - E initial = E products - E reactants
Background image of page 2
Dept. of Chemistry, University of Houston w = 0, so ! E = q If a system does no work but transfers E as heat (q): Here internal E decreases as heat flows out of the system: ! E < 0 so q < 0 ! E > 0 so q > 0 E enters or leaves a system as heat and/or work 5 Ice water gains E as heat from surroundings until T system = T surroundings . © CHEM 1331 Prof. Geanangel, Chapter 6 Dept. of Chemistry, University of Houston q = 0 so ! E = w If a system transfers energy only as work (w): Energy is lost by the system as work, so ! E < 0, and w < 0. Work, where a volume change occurs against an external pressure, is PV work . If external P is then raised , system V decreases, increasing E by doing work on it: ! E >0 and w > 0. A reaction forms a
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/16/2011 for the course BIOL 1361-1362 taught by Professor Any during the Spring '08 term at University of Houston.

Page1 / 21

C6F2009 - Chapter 6 Thermochemistry: Energy Flow and...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online