Year 8 Science • Science inquiry • Questioning and predicting • AC9S8I01

Investigable Questions, Predictions and Hypotheses — AC9S8I01

Good investigations begin with questions that evidence can answer. Patterns and models support reasoned predictions and testable hypotheses—not guesses.

Learning goals
  • Distinguish investigable questions from questions based mainly on values.
  • Identify independent, dependent, controlled and confounding variables.
  • Use patterns and models to make reasoned predictions.
  • Write a directional hypothesis with a scientific reason.
Prerequisite knowledge

Recall that observations describe what is detected, inferences interpret observations, and scientific models represent selected features or relationships.

Key concept

Use the chain pattern or model → investigable question → variables → reasoned prediction or hypothesis → evidence. An investigable question names measurable variables and conditions. Questions such as “Should we…?” or “Is this good?” involve values and cannot be answered by experimental measurements alone.

A correlation means variables change together; causation means changing one produces a change in the other. Controlled investigations help test causation, while a confounding variable provides another possible explanation.

A prediction states an expected outcome. A hypothesis proposes a testable, directional relationship and a reason: If [independent variable changes], then [dependent variable changes], because [scientific reason].

A model may be a diagram, physical object, mathematical relationship or simulation. It can generate questions and predictions even though it simplifies reality; its predictions must still be compared with evidence.

Worked examples
Pattern / modelQuestionVariablesPrediction
Pattern / model → Question → Variables → Prediction: use evidence at every step.

Correlation and causation

Ice-cream sales and sunburn cases both rise in summer, but ice-cream does not cause sunburn. Stronger sunlight and hotter weather influence both, so the pattern alone does not establish causation.

A measurable question

Replace “Why do plants hate salt?” with “How does salt concentration affect the mass of potato tissue after 30 minutes?” Salt concentration is the independent variable and mass change is the dependent variable.

Model-based question

A plate-boundary model can support the question “How does boundary type affect earthquake and volcano patterns?” The model predicts a relationship that mapped observations can test.

Reasoned prediction and hypothesis

If reactant concentration increases, reaction rate should increase because more particles in a given volume increase collision frequency. If light exposure increases within suitable limits, plant growth should increase because light supports photosynthesis.

Common misconceptions
Two variables change together, so one causes the other. Correction: A third variable may explain both.
Any question is scientifically investigable. Correction: The question must be answerable with measurable evidence.
A hypothesis is just a guess. Correction: It is a testable relationship supported by scientific reasoning.
Models must copy reality exactly. Correction: Useful models simplify reality for a stated purpose.
Guided practice
  1. Underline the two measurable variables in a question.
  2. Name which variable is changed and which is measured.
  3. Identify one variable that should be controlled.
  4. Complete an if–then–because hypothesis using a model or known pattern.
Independent practice
  1. Improve the question “Is fertiliser good for plants?” so it is measurable.
  2. Explain why ice-cream sales and sunburn do not establish causation.
  3. Write a reasoned prediction for concentration and reaction rate.
  4. Identify the confounding variable if both light colour and water amount change.
  5. Develop an investigable question from a plate-boundary model.
  6. Explain why a hypothesis is tested rather than proved before an investigation.
Reasoning/problem-solving

Two explanations predict different outcomes when water temperature changes. Design one measurable question and hypothesis that could distinguish the explanations, then identify a confounding variable to control.

Questions and answers
  1. What makes a question investigable? Measurable evidence could answer it under stated conditions.
  2. Prediction or hypothesis? A prediction states an expected result; a hypothesis proposes a testable relationship with reasoning.
  3. Why control variables? To reduce alternative explanations for a change in the dependent variable.
  4. Can a correlation be useful? Yes. It can reveal a pattern worth investigating, but it does not by itself prove causation.
Practice and review
  1. Turn “Do plants like salt?” into an investigable question.
    Name salt concentration, a measurable plant response and a time or method.
  2. Evaluate “More umbrellas cause more rain.”
    Identify correlation, reverse reasoning and weather as the common factor.
  3. Write a hypothesis for light exposure and plant growth.
    Use if–then–because, identify both variables and qualify suitable limits.
Check understanding
  • I write measurable questions.
  • I identify all variable roles.
  • I separate correlation from causation.
  • I justify predictions and hypotheses with science.

Exit ticket: Why can a strong correlation still fail to show causation?

Teacher + parent guidance

Teacher

Move from weak questions to measurable versions, then ask students to name variables and the scientific reason before planning a method.

Parent/carer

Use everyday patterns and ask: What changes, what can we measure, and what else might explain the pattern?

Support: use a variable sentence frame.
Core: justify a directional hypothesis.
Extend: compare causal and correlational questions without drifting into senior statistics.
Curriculum alignment

Australian Curriculum v9.0 — AC9S8I01: develop investigable questions, reasoned predictions and hypotheses to explore scientific models, identify patterns and test relationships.

Victorian Curriculum F–10 Version 2.0 — Levels 7–8, VC2S8I01: Exact.

NSW Science 7–10 Syllabus (2023) — Stage 4, SC4-WS-02: Exact — the NSW Working Scientifically outcome directly align with the core inquiry process.

Broad international closest-topic links include NGSS Practice 1, KS3 Working Scientifically, Ontario Grade 8 STEM investigation skills, New Zealand investigating in science and middle-school NCERT inquiry. These are supportive comparisons, not identical curriculum structures.

FrameworkLevel/StageRelationshipMapping
Australian CurriculumYear 8CanonicalAC9S8I01
Victoria V2.0Levels 7–8ExactVC2S8I01
NSW 2023Stage 4ExactSC4-WS-02
Practice/teaching resources
Official curriculum references
🎥 Optional Video Lesson

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Recommended: Nature of Science

Amoeba Sisters — Develop a testable question and a reasoned hypothesis while recognising that science uses more than one fixed method.

As you watch: What makes a question testable using observations or measurements?

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Try it: Turn a question about seed germination into a testable question. Identify the variable you would change, what you would measure and the reason for your prediction.

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Curriculum equivalents: Victoria, NSW and international

Curriculum equivalents for Develop investigable questions, reasoned predictions and hypotheses to explore scientific...

Mapped skill: develop investigable questions, reasoned predictions and hypotheses to explore scientific models, identify patterns and test relationships

These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.

RegionCurriculum frameworkClosest level or code
AustraliaAustralian Curriculum v9.0AC9S8I01 · Year 8
VictoriaVictorian Curriculum F–10 Version 2.0 — ScienceVC2S8I01 · Levels 7–8
New South WalesNSW Science 7–10 Syllabus (2023)SC4-WS-02 · Stage 4
United States (USA)Next Generation Science Standards (NGSS)Middle School (Grades 6–8)
Canada (Ontario)Ontario Curriculum — ScienceGrade 8
United Kingdom (England)National Curriculum in England — ScienceYear 9, Key Stage 3
IndiaNCERT / CBSE — ScienceClass 8

Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.

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