Identify controlled variable
A fair investigation in a antacid comparison changes temperature and measures reaction time. Which listed factor should be controlled: the result or temperature? Use the visual evidence before giving the chemistry or investigation judgement. Enter the answer and choose the interpretation that matches the chemistry.
Worked practice: chemistry evidence and answer
Use the chemical evidence first, then enter the result and interpretation that match it.
Write a full answer
Now write the response in full, in your own words — this is what the exam asks for. The AI marks it on the same moves you built above (focus, evidence, technique, judgement) and gives feedback on reasoning, evidence, and expression.