Chemistry Year 11 - Module 2 - Lesson 3
Empirical & Molecular Formulas
1. Key Ideas
In the 1800s, chemists could burn a compound and weigh the products — but they had no way to know if glucose (C₆H₁₂O₆) and acetic acid (CH₂O, scaled up) were the same substance or different ones. The empirical formula was the tool they used to bring order to that chaos. It's still the first formula a chemist derives from experimental data today.
- Definition of empirical formula
- Why two compounds can share an empirical formula
2. Success Criteria
By the end, you should be able to:
- Definition of empirical formula
- Definition of molecular formula
- That molecular formula = empirical × n
3. Key Terms
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: "Definition of empirical formula". Use one specific example from the lesson.
2. Apply this idea to a new example: "Definition of molecular formula". Show your reasoning clearly.
3. Analyse why this idea matters for understanding Empirical & Molecular Formulas: "That molecular formula = empirical × n".
6. Extend: Apply the Idea
A student gives a memorised answer about Empirical & Molecular Formulas 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 Empirical & Molecular Formulas?
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 Empirical & Molecular Formulas?
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.