- 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 = -qreaction
- q = the amount of heat absorbed or released
○ Note: “molar heat of solution” = q
- Signage of Heat Transfer Equations:
○ Do q = mcpΔT and keep q always positive initially
○ Add a positive or negarive sign to the q value on the knowledge that…
■ If the temp of the water went down, then the reaction was endothermic and qsol = –
■ If the temp of the water went up, then the reaction was exothermic and qsol = +
- ΔHrxn =
○ Important: ΔH will be per 1 mole of substance → divide moles in sample by moles (coefficient) in the balanced equation
- 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 of sample
○ C = specific heat
○ Questions involving two substances: Do two mcats → mcΔT = – (mcΔT)
■ Ex: 
○ Questions involving ΔT
■ If moles increases → more moles reacting so final temp will be higher → q increases b/c ΔT is greater
■ If heat is lost to the surroundings (ex: air) → q decreases b/c ΔT is smaller → (if exo) ΔH will be less negative
- Example Question Proccess
- Water is heated by an external source (ex: combustion)
- Since water is only thing undergoing temp change, only use the mass of water
- Chemicals are mixed in a solution and a temp change occurs in a solution (calorimetry)
- Use temp change and cp of the solution, and the mass of the solution (mass of solute + solvent)