Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain that a process can be split into a series of steps, real or imagined, and that each step has its own ΔH. (Guide: “One change, more than one route”; Practice Q5)
- I can explain, using conservation of energy, why the ΔH values of the steps add up to the ΔH of the whole process. (Guide: “Why the steps must add up”; Practice Q6)
- I can explain why two different routes between the same start and end must give the same ΔH. (Guide: “Why the steps must add up”; Practice Q6)
- I can explain why a liquid and a gas of the same compound do not cancel in a Hess’s law sum. (Guide: Figure 1; Practice Q7)
Calculation
- I can give ΔH for a reversed equation by changing its sign. (Practice Q1)
- I can give ΔH for an equation multiplied by a whole number or a fraction. (Practice Q1, Q3)
- I can choose which given equations to reverse or scale so they add to a target equation. (Guide: Worked examples 1 and 2; Practice Q2)
- I can cancel substances correctly when the amounts on each side are different, leaving the remainder. (Guide: Worked example 2; Practice Q4)
- I can add a physical step, such as vaporization, to a chemical step to reach a target. (Guide: Figure 1; Practice Q7)
- I can show that ΣΔHf°(products) − ΣΔHf°(reactants) is a route through the elements. (Guide: Worked example 3)
Reasoning
- I can draw or read a Hess cycle or a step energy diagram and use it to find an unknown ΔH. (Guide: Figures 1 and 2; Practice Q5)
- I can judge whether a difference between two measured routes is experimental error, giving a specific source of error. (Practice Q6)
- I can explain why the overall ΔH is negative or positive by comparing energy absorbed in some steps with energy released in others. (Practice Q5)
All ticked? Move on to Topic 7.1, Introduction to Equilibrium, or return to the course roadmap.