Year 9 Science • AC9S9I02 • Authored homework
Valid and Reproducible Investigations
Plan and conduct valid, reproducible investigations by controlling variables, using suitable equipment, repeating trials, managing risk and collecting useful evidence. Use precise science language and support longer responses with clear reasoning.
Part A
Short-answer questions
What does validity mean in a scientific investigation?
What does reproducibility mean?
Why should controlled variables be kept the same?
Why are repeated trials useful?
What is the purpose of a control group or control condition?
Name one risk that should be managed in a heating investigation.
Why should equipment choice match the measurement needed?
What information should be included in a method so another student can repeat it?
How can sample size affect investigation quality?
Correct this misconception: “One successful trial proves the hypothesis.”
Part B
Long-answer questions
Plan a valid investigation into how temperature affects the rate at which sugar dissolves. Include variables, equipment, method, repeats and safety.
A group changes both water temperature and stirring speed. Explain why the investigation is not valid and how to redesign it.
Write a reproducible method for testing how light intensity affects plant growth over two weeks.
Compare a method with one trial to a method with five trials. Explain how repeats affect reliability and confidence.
Explain how risk assessment should change when an investigation uses hot water, glassware, electricity or living organisms.
Design a data table for an investigation that includes repeated trials and a mean. Explain why each column is useful.
Evaluate whether an investigation with a small sample, no control group and vague measurements can support a strong conclusion.
Improve a weak method by adding controlled variables, exact measurements, safety steps and repeat trials.
Explain how validity and reproducibility are different but connected in good science.
Write a full investigation plan for one Year 9 topic, including aim, variables, method, data collection, safety and how results will be checked.
Part C
Research and understanding task
Find or design one simple school investigation. Rewrite it so another class could reproduce it exactly. Include variables, equipment, step-by-step method, repeats, risk controls, data table and how the conclusion should be judged.