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 say which phase changes increase the energy of a system and which decrease it. (Guide: “What happens to energy in a phase change”; Practice Q2)
- I can explain why the temperature of a pure substance stays constant while it melts or boils. (Guide: “Why the temperature stays constant”; Practice Q1)
- I can explain why ΔH_vap is larger than ΔH_fus for the same substance. (Guide; Practice Q6)
- I can state that a phase change and its reverse have molar enthalpies of equal size and opposite sign. (Guide: “Opposite changes, opposite signs”; Practice Q6)
Calculation
- I can calculate the energy absorbed or released in a phase change using q = n × ΔH, converting grams to moles first. (Guide: Worked example 1; Practice Q2)
- I can compare the energy needed to change the phase of equal masses of different substances. (Practice Q3)
- I can find a molar enthalpy of fusion or vaporization from a heating curve or heating data. (Guide: Worked example 3; Practice Q4, Q6)
- I can combine q = mcΔT and q = n × ΔH in a calculation with several steps, keeping units consistent. (Guide: Worked example 2; Practice Q5)
Reasoning
- I can identify each sloping and flat section of a heating or cooling curve and say what is happening to the particles. (Guide: Figure 1)
- I can use an energy balance that includes a phase change to predict a final temperature. (Practice Q7)
- I can explain everyday effects, such as steam burns or ice cooling a drink, using the energy of phase changes. (Practice Q5, Q7)
All ticked? Move on to Topic 6.6, Introduction to Enthalpy of Reaction, or return to the course roadmap.