lecture15 - Lecture 15 Thermochemistry part 2 Internal...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Lecture 15 Thermochemistry, part 2 Internal energy changes The internal energy of a system is the sum of all the KE and PE of all of the components of the system. Changes are defined as final minus initial E = E final -E initial
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 First Law of Thermodynamics The first law of thermodynamics states that the energy gained or lost by a system must equal the energy lost or gained by surroundings. Energy is not created or destroyed Energy is transferred via heat and work The calorie (cal) is the amount of heat necessary to raise the temperature of 1 g of water 1 o C. 1 food “Calorie” = 1000 cal The joule (J) is the SI unit: 4.184 J = 1 cal. E = q + w E = change in system’s internal energy (energy gain is positive) q = heat (heat absorbed is positive) w = work (work done by system is negative) Work done by the system Work is force times distance many types of work, including “PV” work Change in Internal Energy
Background image of page 2
3 Energy flow: heat and work Enthalpy (H) = E + PV Change in Enthalpy ( H) = E + P V At constant pressure q P = E + P V, therefore q P = H H = change in enthalpy: an energy flow as heat (at constant pressure) H > 0, Endothermic; H < 0, Exothermic Enthalpy and Change in Enthalpy
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 Enthalpy for heating Heat Capacities Molar heat capacity (c p ) is the heat required to raise the temperature of 1 mole of a substance by 1 o C at constant pressure. q = nc p T Specific heat (c s ) is the heat required to raise the temperature of 1 gram of a substance by 1 o C at constant pressure. Heat capacity (C p ) is the quantity of heat needed to raise the temperature of some specific object by 1 o C at constant pressure.
Background image of page 4
5 Heat capacities can vary Substance c p (J/mol·°C) Water (s) 37.1 Water (l) 75.3 Ethanol (l) 113.1 Graphite C(s) 8.54 Al, Cu, Fe (s) 24.4, 24.5, 25.1 Specific Heat Capacity: Example A 1.0 gram block of Al (c
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 14

lecture15 - Lecture 15 Thermochemistry part 2 Internal...

This preview shows document pages 1 - 6. Sign up to view the full document.

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