Australian Curriculum v9 / ACiQ Year 9 Science - Unit 3 - Investigable questions, hypotheses and models

Investigable questions, hypotheses and models

Develop testable relationship questions, reasoned predictions and explanatory models.

Updated 2026-07-26 - 11 min read

Investigable questions, hypotheses and models requires students to connect an observable phenomenon with a scientific model, mechanism or evidence chain. A dependable Year 9 explanation names the relevant system, traces what changes, supports the claim with evidence and recognises the limits of the model or investigation.

This note is designed to work with the guided lessons, curated practice, flashcards, Tutor context, Review and Rapid Revision for the same canonical target. The same three evidence checks are used throughout, so feedback can route a learner back to the precise idea that needs repair.

Investigable relationship questions

Not every valuable question is experimental, but the planned evidence must be capable of addressing it.

A dependable reasoning routine

  1. Define the system or phenomenon and identify the change being explained.
  2. Trace the mechanism for investigable relationship questions in causal order rather than listing disconnected terms.
  3. Link each claim to an observation, measurement, model or accepted scientific relationship.
  4. State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: Turn the topic into a measurable relationship with defined variables.

The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.

Example 1.1

Best investigation question?

Step 1 - identify the governing idea: A strong experimental question asks how a changed variable affects a measured variable in a defined system.

Step 2 - apply it to this evidence: Changed and measured variables are explicit.

Result: How does water temperature affect the time for a sugar cube to dissolve?

The evidence-to-mechanism link is: Changed and measured variables are explicit. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • Why is water interesting? — It conflicts with the stated mechanism or evidence: Changed and measured variables are explicit.
  • Tell me about sugar — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Is science useful? — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 1.2

Why is 'Does exercise help?' weak?

Step 1 - identify the governing idea: A strong experimental question asks how a changed variable affects a measured variable in a defined system.

Step 2 - apply it to this evidence: The evidence target is ambiguous.

Result: Help is undefined and variables, group and measure are unclear

The evidence-to-mechanism link is: The evidence target is ambiguous. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • It has a question mark — It conflicts with the stated mechanism or evidence: The evidence target is ambiguous.
  • Exercise cannot be studied — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • All yes/no questions are invalid — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 1.3

A non-experimental question about a distant star can be scientific if?

Step 1 - identify the governing idea: A strong experimental question asks how a changed variable affects a measured variable in a defined system.

Step 2 - apply it to this evidence: Investigability is not limited to classroom manipulation.

Result: Observations or existing data can provide relevant evidence

The evidence-to-mechanism link is: Investigability is not limited to classroom manipulation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • The answer is guessed — It conflicts with the stated mechanism or evidence: Investigability is not limited to classroom manipulation.
  • No evidence is needed — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Only opinions are collected — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Reasoned predictions and hypotheses

It is not made correct by matching results; results support, fail to support or complicate the hypothesis under tested conditions.

A dependable reasoning routine

  1. Define the system or phenomenon and identify the change being explained.
  2. Trace the mechanism for reasoned predictions and hypotheses in causal order rather than listing disconnected terms.
  3. Link each claim to an observation, measurement, model or accepted scientific relationship.
  4. State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: It is a pre-test, reasoned prediction evaluated against evidence.

The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.

Example 2.1

Strong hypothesis for ramp height and car speed?

Step 1 - identify the governing idea: A hypothesis predicts a relationship and justifies it with relevant scientific knowledge.

Step 2 - apply it to this evidence: Direction and mechanism are stated.

Result: If ramp height increases, car speed will increase because more gravitational energy can transfer to kinetic energy

The evidence-to-mechanism link is: Direction and mechanism are stated. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • The car will be fast — It conflicts with the stated mechanism or evidence: Direction and mechanism are stated.
  • Ramp height is interesting — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • I think speed — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 2.2

Results do not match hypothesis. Best response?

Step 1 - identify the governing idea: A hypothesis predicts a relationship and justifies it with relevant scientific knowledge.

Step 2 - apply it to this evidence: Scientific value does not depend on confirmation.

Result: Report the evidence and evaluate method and explanation

The evidence-to-mechanism link is: Scientific value does not depend on confirmation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • Change data — It conflicts with the stated mechanism or evidence: Scientific value does not depend on confirmation.
  • Delete hypothesis — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Claim it was correct — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 2.3

Why specify direction?

Step 1 - identify the governing idea: A hypothesis predicts a relationship and justifies it with relevant scientific knowledge.

Step 2 - apply it to this evidence: A vague association is less informative.

Result: It makes the predicted relationship testable and interpretable

The evidence-to-mechanism link is: A vague association is less informative. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • To guarantee result — It conflicts with the stated mechanism or evidence: A vague association is less informative.
  • To remove controls — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Because direction is a unit — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Develop explanatory models

Models can be diagrams, physical systems, equations or simulations. Their usefulness is judged against purpose and evidence.

A dependable reasoning routine

  1. Define the system or phenomenon and identify the change being explained.
  2. Trace the mechanism for develop explanatory models in causal order rather than listing disconnected terms.
  3. Link each claim to an observation, measurement, model or accepted scientific relationship.
  4. State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: A model may be abstract and should explain or predict within stated limits.

The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.

Example 3.1

What strengthens a particle model of dissolving?

Step 1 - identify the governing idea: An explanatory model identifies relevant entities, relationships, mechanisms and boundaries.

Step 2 - apply it to this evidence: It represents a mechanism.

Result: Showing particles separating, moving and mixing while atoms remain conserved

The evidence-to-mechanism link is: It represents a mechanism. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • Drawing a colourful cup only — It conflicts with the stated mechanism or evidence: It represents a mechanism.
  • Making particles visible in reality — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Removing labels and motion — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 3.2

Why state model boundaries?

Step 1 - identify the governing idea: An explanatory model identifies relevant entities, relationships, mechanisms and boundaries.

Step 2 - apply it to this evidence: Predictions are valid only within represented scope.

Result: To define which parts and interactions are included

The evidence-to-mechanism link is: Predictions are valid only within represented scope. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • To make evidence optional — It conflicts with the stated mechanism or evidence: Predictions are valid only within represented scope.
  • To hide missing data — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Models have no boundaries — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 3.3

A model predicts faster transfer at higher temperature. Useful next step?

Step 1 - identify the governing idea: An explanatory model identifies relevant entities, relationships, mechanisms and boundaries.

Step 2 - apply it to this evidence: Prediction connects model to evidence.

Result: Test the prediction with a valid investigation

The evidence-to-mechanism link is: Prediction connects model to evidence. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

  • Accept without testing — It conflicts with the stated mechanism or evidence: Prediction connects model to evidence.
  • Change model to match preference — It changes the system boundary or claims a cause that the supplied observations do not establish.
  • Ignore variables — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Retrieval check

Try these without looking back at the examples.

  1. Why is 'Does exercise help?' weak?
  2. Results do not match hypothesis. Best response?
  3. Why state model boundaries?

Answers

  1. Help is undefined and variables, group and measure are unclear — The evidence target is ambiguous.
  2. Report the evidence and evaluate method and explanation — Scientific value does not depend on confirmation.
  3. To define which parts and interactions are included — Predictions are valid only within represented scope.

Transfer task

Find an unfamiliar example from school, daily life, a credible news source or another subject. Explain which of the three evidence checks applies. Complete the task, then audit your own response: identify the evidence used, the relationship applied, one plausible misconception and the final reasonableness check. If a peer could not reproduce your reasoning, add the missing step.

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