# AP Chemistry Unit 6.4 Heat Capacity and Calorimetry

Heat Capacity and Calorimetry

• Heat capacity (C): heat absorbed per degree (J/C or J/K)
• Extensive property: depend on amount of substance
• Specific heat capacity (cp): heat capacity per gram (J/C g or J/K)
• Amount of heat required to change one gram of a substance temperature by one degree C or K
• Every substance has its own specific heat capacity
• Cp of water is 4.18 J/C g → requires 4.184 J (1 cal) of energy to heat a gram by one degree
• Molar heat capacity: heat capacity per mol (K/C mol or K/K mol)
• Specific and Molar heat capacity are intensive properties: independent of the amount (of substance)

Heat Transfer Equations

• qA = -qB → heat lost = – heat gained
• qsystem = -qsurroundings; qsolution = -qsurroundings
• Questions involving specific heat → the amount of heat (J) gained/lost by a sample (q) can be determined by the formula: q = mcpΔT or ncpΔT
• M = mass
• C = specific heat
• ΔH = -q
• Questions involving two substances: Do two mcats → mcΔT = – (mcΔT)
• Ex:
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