Australian Curriculum v9 / ACiQ Year 7 Science - Unit 1 - Questions, variables and fair tests

Questions, Variables and Fair Tests | Year 7 Science

Turn observations into testable questions and identify the variables that make an investigation fair.

Updated 2026-06-15 - 4 min read

Science investigations start with a question that can be tested. A good Year 7 investigation does not need expensive equipment, but it does need clear variables and a fair method.

An observation is something you notice. A testable question turns that observation into something you can measure or compare.

From observation to testable question

Observation: Some paper towels seem stronger than others.

Weak question: "Which paper towel is best?"

Better question: "How does paper towel brand affect the number of coins the wet towel can hold before tearing?"

The better question is testable because it names:

  • what will be changed: paper towel brand
  • what will be measured: number of coins held before tearing
  • the situation: wet towel strength

Testable questions often begin with "How does..." because that wording pushes you to connect a change with a measurement.

The three variable types

The independent variable is the thing you deliberately change. In the paper towel example, it is the brand.

The dependent variable is what you measure. It depends on what you changed. In the example, it is the number of coins the towel holds before tearing.

Controlled variables are the things kept the same so the comparison is fair. For the paper towel investigation, these could include towel size, water amount, coin type, waiting time and how the towel is held.

What makes a fair test fair?

A fair test tries to make sure the result is caused by the independent variable, not by some hidden difference in the method.

Suppose one paper towel is tested with 20 mL of water and another with 60 mL. If the second towel tears faster, you cannot tell whether the brand was weaker or the towel was simply wetter. Water amount must be controlled.

Fair testing is about trust. A result is more trustworthy when another student could follow the method and understand why the comparison is fair.

Repeats improve confidence

One trial can be affected by a mistake or unusual result. Repeating trials helps you see whether the pattern is consistent.

If Brand A holds 12 coins once and Brand B holds 13 coins once, that is not much evidence. If Brand A holds 11, 12 and 12 while Brand B holds 18, 17 and 19, the pattern is stronger.

Repeats do not make a poor method fair, but they make a fair method more reliable.

Planning a method

A useful method is specific enough that someone else could repeat it. Instead of "give the plants some water", write "give each plant 20 mL of water every morning".

Good methods also mention safety and risk. Even simple investigations may involve spills, breakages, hot water, sharp tools, allergies or living things that need care.

Quick check

  1. In "How does ramp height affect the distance a toy car travels?", what is the independent variable?
  2. What is the dependent variable?
  3. Name two controlled variables.
  4. Why should the test be repeated?

Answers:

  1. Ramp height.
  2. Distance the toy car travels.
  3. Same toy car, same surface, same starting position or same release method.
  4. Repeats help show whether the result is consistent or just a one-off.

Transfer task

Design a fair test for one of these: paper plane distance, ice melting speed, seed germination, sponge absorbency or ball bounce height. Write the testable question, variables and one risk control.

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