Chemistry Year 11 - Module 4 - Lesson 4

Calorimetry — Dissolution of Ionic Substances

Use this worksheet after reading the lesson to practise the key ideas and prove you can meet the success criteria.

Name

Date

Class

1. Key Ideas

An instant cold pack gets icy the moment you crack it — no freezer, no ice. A bag of white powder and water, and suddenly your ankle is numb. Dissolution calorimetry measures exactly how much energy moves when an ionic lattice breaks apart and its ions disappear into water.

Lattice energy (endothermic) and hydration energy (exothermic) as the two steps of dissolution
Why ΔH soln sign follows from the temperature change direction

2. Success Criteria

By the end, you should be able to:

Lattice energy (endothermic) and hydration energy (exothermic) as the two steps of dissolution
Endothermic examples: NH₄NO₃, NH₄Cl, KNO₃ (cold packs)
Exothermic examples: NaOH, CaCl₂ (warms solution)

3. Key Terms

negativeIf the solution warms (ΔT > 0), dissolution is exothermic → ΔHsoln is negative.

positiveIf you measured a temperature drop, your answer must be a positive ΔHsoln.

Enthalpy change (ΔH)The heat energy exchanged at constant pressure during a reaction.

ExothermicA reaction releasing heat to surroundings (ΔH < 0).

EndothermicA reaction absorbing heat from surroundings (ΔH > 0).

CalorimetryThe experimental measurement of heat changes during chemical processes.

4. Activity: Build the Lesson Map

Use the lesson to complete the table. Keep answers brief but specific.

Prompt	Your answer
Main concept
Important example
Common mistake to avoid
How this links to the next lesson

5. Short Answer Questions

1. Explain this lesson goal in your own words: "Lattice energy (endothermic) and hydration energy (exothermic) as the two steps of dissolution". Use one specific example from the lesson.

Band 32 marks

2. Apply this idea to a new example: "Endothermic examples: NH₄NO₃, NH₄Cl, KNO₃ (cold packs)". Show your reasoning clearly.

Band 43 marks

3. Analyse why this idea matters for understanding Calorimetry — Dissolution of Ionic Substances: "Exothermic examples: NaOH, CaCl₂ (warms solution)".

Band 54 marks

6. Extend: Apply the Idea

Band 5/65 marks

A student gives a memorised answer about Calorimetry — Dissolution of Ionic Substances but does not use evidence or reasoning.

Improve the answer by writing a stronger response that uses accurate terminology, a relevant example and a clear explanation.

7. Multiple Choice

1. What is the best first step when answering a question about Calorimetry — Dissolution of Ionic Substances?

A. Identify the key concept being tested

B. Write every fact from memory

C. Ignore the command word

D. Skip examples and evidence

2. Which answer would show stronger understanding of Calorimetry — Dissolution of Ionic Substances?

A. An answer with accurate terms and reasoning

B. A copied definition only

C. A single-word response

D. An answer with no example

3. What should you do if a question asks you to explain?

A. Link the idea to a reason or cause

B. List unrelated facts

C. Only draw a diagram

D. Write the shortest possible answer

8. Success Criteria Proof

Finish with evidence that you can do each success criterion.

Success criterion 1

Prove that you can: Lattice energy (endothermic) and hydration energy (exothermic) as the two steps of dissolution