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Thermochemistry. Def-Heat gain or loss that occur during chemical or physical changesPhysical change (ex.-boiling, evaporation, etc)Chemical reaction (ex-combustion, combination, etc). Energy. Def-ability to do work or supply heatEnergy can not be observed, only detected because of its effe
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1. Specific Heat Review
2. Thermochemistry Def-Heat gain or loss that occur during chemical or physical changes
Physical change
(ex.-boiling, evaporation, etc)
Chemical reaction
(ex-combustion, combination, etc)
3. Energy Def-ability to do work or supply heat
Energy can not be observed, only detected because of its effects
Only measure changes in energy (heat)
Units- joule (J) or calories (cal)
(also KJ or Kcal)
4. MEASURING AND EXPRESSING HEAT CHANGES Goal is to quantitatively measure heat change
Calorimetry
Def- measurement of the heat released or absorbed in a reaction
Heat lost by the system = heat absorbed by the surroundings (vice versa)
5. THERMOCHEMICAL EQUATIONS A thermochemical equation includes:
balanced chemical equation
the states of matter
term for heat-usually represented as ?H
H2O(l) ? H2O(g) ?H= +40.7 KJ
6. ENDOTHERMIC AND EXOTHERMIC PROCESS Together the system and the surroundings constitute the universe
Law of Conservation of Energy
Energy lost (or gained by the system) = Energy gained (or lost by the environment)
Exothermic reactions = release energy (?H= - or written on the product side)
Endothermic reactions = absorb energy(?H= + or written on the reactant side)
7. SPECIFIC HEAT Def-energy needed to raise the temperature of 1gram of an object by 1oC.
Heat energy measured in
Calories
Joule
q = m x ? T x C Heat (q) - cal or joules
Mass (M) - grams
Temperature (?T) - C
Specific heat (C) cal/gC or j/gC
8. Heat of Fusion/Vaporization Def-energy needed to go through a phase change (solid to liquid/liquid to solid or liquid to vapor/vapor to liquid).
Heat energy measured in
Calories
Joule
q = m x Hfusion or q = m x Hvaporization Heat (q) - cal or joules
Hfusion liquid to solid/solid to liquid = 334 J/g (for water)
Hvaporization liquid to vapor/vapor to liquid = 2260 J/g (for water)
9. Phase change diagram Graph compares the temperature and the heat energy (or time as energy increases) 1 solid phase 2 melting/freezing 3 liquid 4 boiling/vaporization 5 - gas