Australian Curriculum v9 / ACiQ Year 10 Science - Unit 1 - Experimental design and evaluation
Experimental Design and Evaluation | Year 10 Science
Design and evaluate investigations using variables, controls, risk, limitations and improvements.
Updated 2026-06-15 - 4 min read
Year 10 Science is where practical work starts to look more like senior science. You still need variables and fair testing, but you also need to justify method choices, discuss limitations and suggest improvements that match the evidence.
Good experimental design answers two questions: what are we testing, and why is this method trustworthy enough?
Start with the relationship
Most experiments test how one variable affects another.
Example question:
"How does acid concentration affect the rate of reaction between hydrochloric acid and magnesium?"
Independent variable: acid concentration.
Dependent variable: reaction rate, perhaps measured by time taken to produce a fixed volume of gas.
Controlled variables: magnesium length or mass, acid volume, temperature, equipment setup and endpoint rule.
The method should make this relationship visible while reducing other explanations.
Controls are not decoration
Controlled variables matter because they protect validity. If magnesium length changes between trials, reaction rate might change because of surface area rather than acid concentration.
When writing a method, do not only list controls. Explain the important ones.
Weak: "Keep everything the same."
Stronger: "Use the same mass and shape of magnesium each trial so surface area does not become a second independent variable."
Repeats, range and intervals
Senior-style investigations need enough data to show a pattern.
Range means the spread of independent variable values. Intervals are the gaps between those values.
Testing only 1 percent and 5 percent acid concentration gives limited evidence. Testing 1 percent, 2 percent, 3 percent, 4 percent and 5 percent gives a better pattern.
Repeats help reliability. If each concentration is tested three times, you can calculate a mean and notice unusual results.
Limitations are not just mistakes
A limitation is a weakness in the design or evidence that affects the strength of the conclusion. It is not the same as a random accident.
Examples:
- only a small range of temperatures tested
- endpoint judged by eye
- heat loss to the surroundings
- sample size too small
- measuring tool not precise enough
An error like "I spilled the liquid" may explain one bad trial, but it is not usually the most useful evaluation point unless it affected the data.
Improvements must match limitations
A good improvement fixes a named limitation.
Limitation: reaction endpoint was judged by eye.
Improvement: use a gas syringe or pressure sensor to measure gas production more objectively.
Limitation: temperature changed during the reaction.
Improvement: use a water bath and monitor temperature during each trial.
Risk and ethics
Risk management is part of experimental design. Identify the hazard, possible harm and control.
Hazard: hot water.
Risk: burns.
Control: use a heatproof mat, tongs or lower temperature range under teacher supervision.
If living things are involved, include ethical care: minimise harm, provide suitable conditions and follow school procedures.
Quick check
- Why should magnesium mass be controlled in a reaction-rate experiment?
- What is the difference between a limitation and an improvement?
- Why are repeats useful?
- Give one example of a measurable control.
Answers:
- Different magnesium amounts could change reaction rate, making the test less valid.
- A limitation identifies a weakness; an improvement explains how to reduce that weakness.
- Repeats show whether results are consistent and help identify unusual data.
- Example: keep temperature at $25^\circ\text{C}$.
Transfer task
Choose a Year 10 practical topic: reaction rate, insulation, plant growth, motion, circuits or enzymes. Write a research question, variables, two controls with reasons, one risk control, one limitation and one matching improvement.