Why this chapter matters
Energy accounting links microscopic bond changes to measurable temperature change and process feasibility.
What you will learn
- Use q = mcDeltaT to calculate heat transfer in a simple calorimetry setup.
- Interpret endothermic and exothermic processes using enthalpy sign conventions.
- Apply Hess's law and standard enthalpies of formation to compute reaction enthalpy.
Lessons in this chapter
- System, surroundings, and energy flowDefine sign conventions and distinguish heat from temperature.
- Calorimetry calculationsSolve heat-transfer problems with mass, specific heat, and DeltaT.
- Enthalpy and reaction profilesUse energy diagrams to classify and compare reaction pathways.
- Hess's law and formation dataCombine equations or tabulated values to find DeltaH for target reactions.
Study task
Complete a thermochemistry packet that includes one calorimetry problem, one Hess's-law combination, and one interpretation of a reaction energy diagram.
Chapter checkpoint
A 100.0 g sample of water warms by 5.0 C. Using c = 4.184 J/(g C), what is q for the water?
q = mcDeltaT = (100.0 g)(4.184 J/(g C))(5.0 C) = 2092 J, positive for the water because it gains heat.