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Specific Heat Review

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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Specific Heat Review

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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

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