Centre for Foundation Studies, UTAR

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Chapter Scopes
• Endothermic & Exothermic reactions
• Enthalpy changes: ∆H of formation, combustion, hydration, neutralization, atomization. CHAPTER 5

Chemical Energetic /
Thermochemistry

• Lattice energy, electron affinity
• Heat of fusion and vaporization
• Hess’ Law
• Born-Haber cycles
• Calorimetry

© 2006 Brooks/Cole - Thomson

© 2006 Brooks/Cole - Thomson

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Energy & Chemistry

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Thermochemistry
• Thermochemistry is the study of heat (energy) change/transfer in a chemical reaction.

• ENERGY is the capacity to do work or transfer heat. • HEAT is the transfer of thermal energy between two objects because of their difference in temperature.

Heat energy is associated with molecular motions.

Other forms of energy light electrical kinetic and potential

Heat transfers until thermal equilibrium is established. ∆T measures energy transferred.

© 2006 Brooks/Cole - Thomson

© 2006 Brooks/Cole - Thomson

System and Surroundings

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System and Surroundings

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Vacuum jacket • SYSTEM
– The object under study • SURROUNDINGS
– Everything outside the system
© 2006 Brooks/Cole - Thomson

FHSC1114 Physical Chemistry

open
Exchange: mass & energy

closed energy isolated nothing © 2006 Brooks/Cole - Thomson

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Centre for Foundation Studies, UTAR

Directionality of Heat Transfer

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Directionality of Heat Transfer

• Heat always transfer from hotter object to cooler one.

• Heat always transfers from hotter object to cooler one.

• EXOthermic: heat transfers from SYSTEM to
SURROUNDINGS.

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• ENDOthermic: heat transfers from
SURROUNDINGS to the SYSTEM.

T(system) goes down
T(surr) goes up
© 2006 Brooks/Cole - Thomson

T(system) goes up
T(surr) goes down
© 2006 Brooks/Cole - Thomson

UNITS OF ENERGY