Recording Observations
How to record chemical observations for IGCSE Chemistry 0620 Paper 6 including colour changes, gas production, precipitates, and temperature changes.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Why this skill matters
Recording observations accurately is the foundation of practical chemistry and is heavily tested on Paper 6. Each observation typically scores 1 mark, and a single experiment may have 4-6 observation marks. Students lose these marks by writing conclusions instead of observations, using vague language, or missing key details like colour changes.
Method and technique
Types of observation
Colour changes: State the initial colour and the final colour. “Blue solution turned colourless” is correct. “The colour changed” is too vague to score.
Gas production: Describe effervescence (bubbles of gas). If you can identify the gas by a test, record the test and its result separately: “gas produced which extinguished a burning splint” (observation) and “gas is carbon dioxide” (conclusion).
Precipitate formation: State that a precipitate formed and describe its colour: “a white precipitate formed”, “a brown precipitate formed”. If the precipitate dissolves on adding excess reagent, note that too.
Temperature changes: Record the actual temperatures, not just “it got hotter”. “Temperature increased from 22 degrees C to 35 degrees C” is a proper observation. “The reaction was exothermic” is a conclusion.
Dissolving: “The solid dissolved to form a colourless solution” or “The solid did not dissolve, it remained as a white powder.”
No visible reaction: If nothing happens, record it: “no visible change” or “no reaction observed”. This is a valid observation and earns a mark when the expected answer is indeed no change.
Recording format
On Paper 6, observations are usually recorded in a two-column table:
| Test | Observation |
|---|---|
| Add NaOH(aq) to the solution | A blue precipitate formed |
| Add NaOH(aq) in excess | The precipitate did not dissolve |
| Heat the precipitate | The precipitate turned black |
Precision in colour descriptions
Use specific colour terms. The mark scheme distinguishes between:
- White, cream, yellow, orange, brown, red, blue, green, purple, black
- “Colourless” (for solutions) vs “clear” (clear means you can see through it; a coloured solution can be clear)
- “Turned from X to Y” (not just “changed colour”)
Common errors and how to avoid them
Writing conclusions instead of observations: “Copper ions are present” is a conclusion. “A blue precipitate formed” is the observation. Keep them separate.
Vague descriptions: “It reacted”, “something happened”, “there was a change” earn zero marks. Be specific about what changed.
Confusing colourless with clear: Water is colourless (no colour) and clear (transparent). Copper sulfate solution is blue and clear. A precipitate makes a solution cloudy/opaque, not coloured.
Missing the “no change” observation: If a test produces no visible change, write it down. A blank cell in the observation column scores zero, but “no visible change” scores a mark when that is the expected answer.
Forgetting initial colours: “The solution turned green” is less precise than “the solution changed from blue to green”. The initial colour confirms you observed the whole process.
Marking points examiners look for
- Specific descriptions (colour, state, temperature with values)
- Initial and final states described for changes
- Observations separated from conclusions
- Correct colour terminology (colourless, not clear, for solutions)
- “No visible change” recorded when nothing happens
- Gas tests recorded as observation + result (not just the conclusion)
Studying this yourself? Tutoring arrangements are normally made by a parent or guardian. Message us for the details to share with them, or send them this page.