Investigable Questions, Reasoned Predictions and Hypotheses

Core idea: strong investigations begin with clear questions. Students decide whether questions can be investigated through systematic evidence, use models and prior knowledge to refine questions, identify variables, make reasoned predictions and construct hypotheses that evidence can support or challenge.

E1 — Investigable questions

An investigable question can be answered using systematic observations, measurements, experiments or appropriate evidence. It should be clear and feasible using available school or web-based resources. A question may be non-investigable as written if it is opinion-based, too broad, ambiguous, unsafe or not feasible.

Useful pattern: “How does [independent variable] affect [dependent variable]?”

E2 — Consulting First Nations Australians

First Nations Australians hold diverse, place-based ecological knowledges developed through long-term observation, practice and knowledge transmission. Relevant knowledge holders can help clarify questions about local patterns such as seasons, tides, species interactions or invasive species. Keep knowledge connected to the specific community and Place, use respectful consultation and attribution, and avoid treating all First Nations knowledges as one identical system.

E3 — Scientific models

A scientific model is a simplified representation used to explain, predict or investigate a system. Models can suggest relationships worth testing. The particle model can guide questions about gases and states of matter; an Earth–Moon–Sun model can guide questions about repeating tide patterns.

E4 — Testing relationships

The independent variable (IV) is deliberately changed, the dependent variable (DV) is measured, and relevant controlled variables are kept consistent. Example: “How does balloon volume change as temperature changes?”

E5 — Reasoned predictions and hypotheses

A reasoned prediction states what is expected and gives a scientific reason before results are known. A hypothesis proposes a testable relationship or explanation. Scaffold: If… (IV), then… (DV), because… (scientific reason).

E6 — Formulating hypotheses

Example: “If parachute surface area decreases, descent time will decrease because a smaller area produces less air resistance.”

Exam sequence

Question → variables → scientific model/knowledge → prediction → hypothesis → evidence.

• Content description: develop investigable questions, reasoned predictions and hypotheses to explore scientific models, identify patterns and test relationships
• E1: discuss features of investigable and non-investigable questions, considering school and web-based resources
• E2: consult with First Nations Australians to clarify questions based on traditional ecological knowledges, such as invasive-species impacts
• E3: develop investigable questions to explore scientific models such as particle theory
• E4: develop investigable questions to test relationships such as balloon volume with heating/cooling and tide height through the lunar cycle
• E5: discuss reasoned predictions and hypotheses and use scaffolds to develop hypotheses
• E6: formulate hypotheses such as the parachute surface-area and air-resistance example

1. What makes a question investigable?

   It can be answered using systematic evidence and is clear and feasible enough to identify what will be observed or measured.

2. Why can an opinion question be non-investigable?

   Opinions cannot usually be resolved by scientific measurement or observation.

3. How can First Nations ecological knowledges refine a question?

   Long-term, place-based observations can reveal patterns, timing and ecological relationships that make a question more precise and locally meaningful.

4. Why must First Nations knowledges be used in context?

   Knowledges are connected to particular communities, Countries/Places, responsibilities and protocols; generalising can misrepresent them.

5. What is a scientific model?

   A simplified representation that helps explain, predict or investigate features of a system.

6. What is the difference between IV and DV?

   The IV is deliberately changed; the DV is measured as the response.

7. Why control variables?

   Controls reduce alternative explanations so changes in the DV can be linked more confidently to the IV.

8. What makes a prediction reasoned?

   It states an expected outcome and justifies it using relevant scientific knowledge or a model.

9. How is a hypothesis different from a prediction?

   A prediction states an expected outcome; a hypothesis proposes a testable relationship or explanation.

10. What is a useful hypothesis structure?

    If [IV changes], then [DV changes], because [scientific explanation].

• Assuming every “why” question is automatically non-investigable.
• Changing more than one independent variable at once.
• Confusing IV and DV.
• Writing a prediction without scientific reasoning.
• Calling any If–then sentence a hypothesis without an explanatory relationship.
• Changing a prediction after seeing results.
• Treating a scientific model as a perfect copy of reality.
• Generalising one First Nations community’s knowledge to all First Nations Australians.

Key definitions

• Investigable question: answerable through systematic evidence.
• Scientific model: simplified representation used to explain, predict or investigate.
• IV: variable deliberately changed.
• DV: variable measured.
• Controlled variables: relevant factors kept consistent.
• Reasoned prediction: science-based expected outcome.
• Hypothesis: testable explanatory relationship.

Fast check

Ask: What evidence would answer this? Can it be observed or measured? Is the question clear and feasible? Can the evidence be checked or repeated?

Prediction vs hypothesis

Prediction: “The balloon will expand when heated because gas particles move faster.”
Hypothesis: “If gas temperature increases, then balloon volume will increase because faster-moving particles collide with the balloon walls more strongly.”

First Nations knowledge reminder

Use specific, respectful wording such as relevant local First Nations knowledge holders and name the community where appropriate. Do not imply one universal First Nations knowledge system.

Quick practice

1. Rewrite “Why do plants grow?” as a measurable relationship question.
2. For “How does water temperature affect dissolving time?”, identify IV, DV and two controls.
3. Write a reasoned prediction for heating a balloon using the particle model.
4. Write a hypothesis for parachute area and descent time.

• AC9S7I02 — Plan and conduct reproducible investigations
• AC9S7U02 — Models and ecosystems
• AC9S7H04 — Science communication