CC15 Heat energy changes in reactions mind map

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CC15 Heat energy changes in reactions mind map

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Energy transfer

Exothermic: System → surroundings; surrounding temperature can rise
Endothermic: Surroundings → system; surrounding temperature can fall
Evidence: Combustion often exothermic; dissolving depends on substance
Reverse reaction: Opposite energy change and sign

Measurement

Cup method: Measured reagents; insulate / lid; record maximum or minimum
ΔT: Final relevant temperature − initial temperature
Fair comparison: Control amounts, concentration, start temperature; repeat
Uncertainty: Heat exchange reduces observed change; safe reagents / resolution

Profiles / bonds

Axes / barrier: Energy versus reaction progress; reactant level → peak = Eₐ
ΔH: Products − reactants; negative exothermic / positive endothermic
Catalyst: Lower peak; starting / ending levels unchanged
Breaking bonds: Requires energy; forming bonds releases energy
Net transfer: Compare energy absorbed breaking and released forming

Calculations · Higher

Average energies: kJ mol⁻¹; estimates; count bonds and equation coefficients
Subtract: ΔH ≈ total broken − total formed
HCl example: 679 − 862 = −183 kJ mol⁻¹ for H₂ + Cl₂ → 2HCl
Water / methane: Count double bonds correctly; include coefficients
Per mole / sign: Adjust to requested product amount; keep negative sign

Connections

Energy transfer → Profiles / bonds: Reaction-profile level changes show overall energy transfer.
Profiles / bonds → Calculations · Higher: Breaking minus forming estimates the energy change.