If a practical question says “explain” and you write the method in order, you have described the procedure. The marks are usually for the reasons, the observations and the conclusion, not the list of steps.
This page helps when you know the practical but your answers still miss marks. For the skill of separating what you see from what you conclude, see writing observations separately from inferences.
What does it sound like when this happens?
Students describe it in similar words.
- “I wrote every step and still only got half the marks.”
- “The mark scheme has points I never thought to write.”
- “I do not know what counts as a reason.”
What is usually behind it?
Practical work at school is taught as steps to follow, so the steps are what students remember. The reasons are assumed, never said aloud. When a written question asks for the reasons, nothing has been practised.
Another cause is mixing observations and inferences in one sentence, so neither can be credited cleanly.
How do you build an explanation answer?
Use a four-part pattern for each stage of the experiment.
| Part | Question to ask |
|---|---|
| Step | What is done? |
| Reason | Why is it done? |
| Observation | What is seen? |
| Inference | What does it show? |
Worked example: heating copper(II) carbonate
Here is a question: “Green copper(II) carbonate is heated and the gas is passed into limewater. Explain what happens.”
The procedure answer says: “Heat the solid, pass the gas into limewater, and watch.”
The explanation answer is built part by part.
| Part | Content |
|---|---|
| Step | The green solid is heated strongly, and a delivery tube leads the gas into limewater |
| Reason | The tube carries the gas into the limewater so it can be tested |
| Observation | The green solid turns black, and the limewater turns milky |
| Inference | Carbon dioxide is given off, and black copper(II) oxide is left |
The full equation is CuCO₃ → CuO + CO₂. The answer names the change in the solid, links the milky limewater to carbon dioxide and finishes with the reaction.
What can you do this week?
- Choose three practicals from your notes.
- For each, fill in the step, reason, observation, inference table from memory.
- Check against your textbook and mark what you missed.
- Repeat with a fresh practical until the reasons come without prompting.
The claim evidence and explanation revision desk helps you rework an answer. The lesson on identifying variables in a chemical investigation covers the planning side.
When might one-to-one tuition help?
If you keep writing steps after you know the pattern, a teacher can mark a real answer of yours and show which sentences are procedure. Hearing it line by line makes the habit easier to change.
See online one-to-one Chemistry tuition for how starting works. Keep a mistake log to see whether the same marks go missing each time.