If you know Science facts but cannot answer open-ended questions, the missing skill is often explanation rather than memory. Open-ended questions require you to select the relevant scientific idea, connect cause to effect, use the evidence in the question, and state the relationship clearly enough for the marker to see the reasoning.
Practise building answers around a simple chain: what happened, what scientific mechanism explains it, and how that mechanism produces the observed result. Avoid dumping every fact you know. A shorter answer with the correct causal link is usually stronger than a longer answer that never connects the science to the question.
Use the Science Learning Hub for subject routes and the Examinations & Assessment Hub for answer precision under examination conditions.