Australian Curriculum v9 / ACiQ Year 7 Science - Unit 1 - Testable questions, hypotheses and variables

Testable questions, hypotheses and variables

Develop testable questions and reasoned hypotheses, then identify independent, dependent and controlled variables.

Updated 2026-07-24 - 8 min read

Develop testable questions and reasoned hypotheses, then identify independent, dependent and controlled variables. This note connects the core scientific model to a worked example, an inquiry design and the limits of the evidence.

Core model

Question → hypothesis → variable roles → evidence. The question names the relationship; the hypothesis predicts it with a reason; the method turns each variable into a deliberate change, measurement or control.

Accessible diagram description: A left-to-right flow shows an observation leading to a testable question, then a reasoned hypothesis. Three branches below the question are labelled independent variable (changed), dependent variable (measured) and controlled variables (kept consistent).

A model is useful because it highlights relationships that help explain or predict evidence. It is not a perfect copy of reality. Always state what the representation includes, what its arrows or symbols mean, and one relevant limitation.

Authored representation workshop

From an observation to testable evidence

Accessibility description: A four-stage flow runs from observation to testable question to reasoned hypothesis to investigation. The question and hypothesis both name water temperature as the changed factor and dissolving time as the measured outcome.

Represented parts

  • Sugar appears to dissolve at different rates
  • How does water temperature affect dissolving time?
  • Warmer water will reduce dissolving time because particles move faster
  • Change temperature; measure time; control volume and cube size

Represented relationships

  • Sugar appears to dissolve at different rates -> How does water temperature affect dissolving time? (focus a measurable relationship)
  • How does water temperature affect dissolving time? -> Warmer water will reduce dissolving time because particles move faster (predict and explain)
  • Warmer water will reduce dissolving time because particles move faster -> Change temperature; measure time; control volume and cube size (operationalise variables)

Learner action: Trace the flow from observation to investigation. Identify the two variables that must remain consistent in both the question and hypothesis, then explain what role each variable has in the investigation.

Dissolving-time trials

Accessibility description: Dissolving time generally decreases as water temperature rises. The 240-second trial at 35 degrees Celsius is much slower than nearby values and should be checked rather than silently removed.

| Water temperature (degrees Celsius) | Trial 1 (s) | Trial 2 (s) | Trial 3 (s) | | --- | --- | --- | --- | | 20 | 184 | 178 | 178 | | 35 | 111 | 240 | 105 | | 50 | 70 | 73 | 73 |

*Equal-sized sugar cubes in 100 mL of water; no stirring.*

Learner action: Repair a partially specified dissolving investigation: write the testable question and matching reasoned hypothesis, operationalise water temperature and dissolving time, define the endpoint, add controlled variables, repeats and the supplied risk control, then design the results table before interpreting the supplied trials.

The representation and table are supplied evidence. Do not replace a represented value, relationship or anomaly with an expected result. If a visual version is created, preserve this text-equivalent information and define every symbol, arrow, heading and unit.

Worked example

The reasoning routine is:

  1. identify the observation, measurement or represented relationship
  2. select the relevant science idea
  3. connect the idea to the evidence in a complete sentence
  4. qualify the answer when the evidence or model has a boundary

Inquiry connection

Question: How does water temperature affect the time one equal-sized sugar cube takes to dissolve without stirring?

Reasoned hypothesis: If water temperature increases, dissolving time will decrease because particles move and mix more rapidly.

  • Independent variable: water temperature
  • Dependent variable: dissolving time
  • Relevant controls: water volume and sugar-cube size
  • Hazard: hot water can burn skin
  • Risk control: use teacher-approved warm water and handle containers away from bench edges
  • Reproducibility detail: state temperatures, water volume, cube size, timing rule and repeat count

Possible data finding: mean dissolving time fell from 180 s at 20 °C to 72 s at 50 °C, with one 240 s result at 35 °C.

Evidence-based interpretation: The overall decrease supports the hypothesis, but the anomalous 35 °C result should be checked.

Limitation: Only one sugar brand was tested, so the result may not transfer to different cube sizes or compositions.

This investigation frame recurs across Year 7 Science. A sound response names a testable relationship, matches the hypothesis to the same variables, manages a realistic risk, specifies quantities and measurement rules, analyses the full data pattern, supports a claim with evidence and states what the evidence cannot establish.

Common errors and corrections

  • Error: Writing a topic instead of a testable question. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Using a prediction without a scientific reason as a complete hypothesis. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Calling the measured outcome the independent variable. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Listing irrelevant controls while missing a factor that could affect the outcome. Correction: Return to the core model and identify the exact evidence or relationship before answering.

Practice

  1. Rewrite 'Which cup is best?' as a measurable question.
  2. Write a reasoned hypothesis for ball drop height and rebound height.
  3. Identify the three variable roles in a plant-growth investigation.
  4. Name one assumption and explain how it could limit interpretation.

Transfer task

Apply the topic to the investigation below without relying on a teacher or AI to mark the reasoning.

Evidence status: activity only. Use the task-specific rubric below for self-review or teacher feedback; completion does not automatically award mastery.

Context: How does water temperature affect the time one equal-sized sugar cube takes to dissolve without stirring?

  1. Rewrite the question if it does not clearly name the relationship and measurable outcome.
  2. Write the matching reasoned hypothesis: include the expected direction and the science idea that justifies it.
  3. Identify the independent variable, dependent variable and at least three relevant controlled variables.
  4. Write a six-step reproducible method. Include equipment, quantities, units, an ordered measurement rule and at least three repeated trials for each condition.
  5. State the hazard, possible harm and a practical control. The control must address the stated hazard rather than being generic advice.
  6. Design a results table with headings and units. State which graph or other representation would best show the relationship and why.
  7. Use this possible finding: mean dissolving time fell from 180 s at 20 °C to 72 s at 50 °C, with one 240 s result at 35 °C. Describe the overall pattern, identify any anomaly and state a reasonable check.
  8. Write a conclusion using claim, specific evidence and scientific reasoning. Finish with this limitation: Only one sugar brand was tested, so the result may not transfer to different cube sizes or compositions.

Correction guide: Compare the question and hypothesis to confirm they use the same two variables. In the method, circle every quantity and unit and underline every controlled condition. In the data response, separate the broad pattern from any anomalous result. In the conclusion, highlight the evidence sentence and box the limitation. If one of these parts is absent, revise that part before checking the scientific vocabulary.

An excellent transfer response is precise without pretending the evidence is perfect. It makes the chain from question to method to data to claim visible, and it explains how the core model applies in the unfamiliar context.

Task-specific inquiry rubric

  • Question and hypothesis for water temperature and dissolving time: Names the same measurable relationship in both and gives a scientific reason. Revise if needed: Align the changed factor, measured outcome and predicted direction.
  • Fair, safe and reproducible method: Controls water volume and sugar-cube size, manages "hot water can burn skin", and specifies quantities, units, measurement rules and repeats. Revise if needed: Replace vague directions and generic safety advice with operational detail.
  • Data and analysis plan: Provides labelled headings and units, an appropriate representation, a way to describe the whole pattern and a rule for checking anomalies. Revise if needed: Show how evidence will answer the question before collecting it.
  • Scientific interpretation and boundary: Links the expected evidence to testable questions, hypotheses and variables and anticipates this boundary: Only one sugar brand was tested, so the result may not transfer to different cube sizes or compositions. Revise if needed: Explain the science link and state what the design cannot establish.

Self-check

For each response, check:

  • Did I use the correct scientific vocabulary?
  • Did I refer to the specific evidence, feature or data?
  • Did I explain the link rather than only naming it?
  • Did I avoid claiming more than the model or data support?
  • If an investigation is involved, did I address question, hypothesis, variables, safety, reproducibility, data, evidence and limitations?

Sources