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Keeping Other Relevant Conditions the Same | Singapore Primary Science Guide

eduKate Learning Manual — Scientific Inquiry

Teaching goal: By the end of this manual, a learner should be able to identify which other conditions need to remain consistent in a fair comparison, explain why they matter, and avoid controlling irrelevant details simply because they appear in the setup.

WAIT, WHAT? Keeping More Things the Same Can Make an Investigation Worse

If a condition cannot reasonably affect the outcome, controlling it adds work without protecting the comparison. A fair test is not a contest to keep the longest list of things identical. It is an attempt to prevent plausible competing causes from changing alongside the factor being investigated.

The useful question is therefore: If this condition changed, could it alter the outcome or the way we measure it?

Children are often taught one sentence about fair tests:

Keep everything else the same.

It is a useful starting point, but it is not quite how real scientific reasoning works.

We do not need to keep literally everything the same. We need to keep other relevant conditions as consistent as reasonably possible so that they do not become alternative explanations for the result.

That word — relevant — is where the thinking begins.

1. The Big Idea: Control Competing Explanations

Suppose we want to know how the amount of water affects seedling growth.

If one seedling receives more water but also receives more light, grows in richer soil and starts much taller, then any difference in growth has several possible causes.

Keeping relevant conditions the same reduces these competing explanations.

Control is not about making the setup neat. It is about making the evidence easier to interpret.

2. What Counts as a Relevant Condition?

A condition is relevant when changing it could reasonably influence the outcome.

For a plant-growth comparison, relevant conditions may include:

  • plant species or variety;
  • starting size and age;
  • soil type and amount;
  • container size;
  • light conditions;
  • temperature and location;
  • observation period;
  • measuring method.

The colour of the ruler used to measure the plant is unlikely to affect plant growth. It does not need to be controlled merely because it is part of the investigation.

3. The Relevance Test

When deciding whether something should be kept the same, ask:

If this condition changed, could it reasonably change the outcome?

If yes, it may need to be controlled.

If no, controlling it probably adds complexity without improving the comparison.

This is much better than memorising a fixed list of “control variables” because relevance changes with the scientific question.

4. The Same Condition Can Be Changed in One Experiment and Controlled in Another

Scientific roles depend on the question.

Suppose we investigate:

How does light duration affect seedling growth?

Light duration is the factor deliberately changed. Water amount should be kept similar.

But if we investigate:

How does water amount affect seedling growth?

Water amount becomes the changed factor, and light duration should now be kept similar.

The object is not permanently a “changed variable” or a “control variable”. Its role comes from the question.

5. Worked Example: Shadow Investigation

Question: How does the distance between a torch and an object affect the size of the shadow formed on a screen?

Relevant conditions to keep consistent may include:

  • the same torch;
  • the same object;
  • the same object orientation;
  • the same screen;
  • the same general alignment;
  • the same method for measuring shadow size.

Now consider the colour of the table. Unless it changes the ability to see and measure the shadow, it is probably not an important condition for the causal comparison.

6. Worked Example: Evaporation

Question: How does exposed surface area affect the amount of water lost by evaporation over two hours?

Possible relevant conditions include:

  • same starting amount of water;
  • same water temperature at the start;
  • same location;
  • same observation duration;
  • similar air movement and surrounding temperature;
  • same method of measuring water loss.

If one container is under a fan and another is not, air movement becomes a competing explanation for a difference in evaporation.

7. ‘As Consistent as Reasonably Possible’

Real investigations are rarely perfect.

Two leaves are not biologically identical. Two containers may differ slightly. Room temperature may change over time. Instruments have limits.

Scientific control therefore does not mean pretending perfect sameness has been achieved. It means designing the investigation so that important competing factors are reduced, monitored or acknowledged.

This is also why limitations matter. A careful learner can say:

“The seedlings were similar but not identical, so natural variation may have affected the result.”

8. Common Misconceptions — and Repairs

  • “Everything must be exactly the same.” Repair: the factor being investigated must differ, and only relevant competing conditions need control.
  • “Control variables are a memorised list.” Repair: decide relevance from the question and mechanism.
  • “If I control many things, the experiment must be good.” Repair: controlling irrelevant details cannot rescue a poor question or wrong outcome.
  • “Natural variation means fair tests are impossible.” Repair: use similar samples, repeats and cautious conclusions.
  • “A condition is either always controlled or always changed.” Repair: its role depends on the question.
  • “Control means the experiment proves cause.” Repair: better control strengthens causal interpretation, but evidence should still be judged within the limits of the method.

9. Teach It: The ‘Could It Affect the Result?’ Game

Use one investigation question, such as:

How does water amount affect seedling height over one week?

Call out conditions one by one:

  • soil type;
  • plant species;
  • ruler colour;
  • light duration;
  • container size;
  • student’s shirt colour;
  • starting seedling height;
  • measurement time.

The learner must answer only after explaining whether the condition could reasonably influence growth or measurement.

This teaches control as reasoning rather than ritual.

10. Guided Practice

For each question, name two important conditions to keep consistent.

  1. How does distance from a light source affect shadow size?
  2. How does exposed surface area affect evaporation?
  3. How does number of identical cells affect bulb brightness?
  4. How does spoon material affect the rate of warming at the handle?

There may be several defensible answers. A strong answer explains why each chosen condition could affect the outcome.

11. Independent Challenge: Find the Hidden Confounder

A learner compares evaporation from two trays. Tray A has a larger exposed surface area but is placed beside an open window. Tray B has a smaller exposed surface area and is placed in a still corner of the room.

The learner concludes that the larger surface area caused faster evaporation.

Explain why the conclusion is weak and redesign the comparison.

A strong answer should identify air movement or location as an additional relevant difference and propose keeping environmental conditions more similar while changing only exposed surface area.

12. How an Adult Should Teach This

  • Ask “Could this other difference also affect the outcome?”
  • Do not praise long lists of controls unless the child can justify them.
  • Use deliberately silly irrelevant examples to sharpen relevance.
  • Use real-world limitations to teach humility rather than pretending every school experiment is perfect.
  • When the child spots a confounder, ask how to redesign the method.

13. What Mastery Looks Like

  • Beginning: repeats “keep everything the same” without identifying what matters.
  • Developing: names common relevant conditions in familiar investigations.
  • Secure: justifies why a condition should or should not be controlled.
  • Strong: detects hidden competing changes and redesigns the method.
  • Advanced for Primary: can discuss natural variation and explain why control improves but does not make evidence perfect.

14. Continue the Scientific Inquiry Sequence

15. Trusted References

eduKate Learning Manual principle: Keep the conditions that could compete with your explanation as stable as you reasonably can. Control exists to protect meaning.

Latest-Standard Strengthening — The Competing-Cause Test

A condition needs control when changing it could create a plausible alternative route to the same outcome. Ask: If this condition differed between groups, could I still tell whether the intended changed factor caused the observed difference? If the answer is no, that condition needs to be kept comparable, monitored or explicitly acknowledged.

Reversal and Position-Swap Check

Some hidden influences are tied to position rather than the object being tested. Where practical, repeat the comparison after swapping positions while preserving the intended conditions. If the result follows the position, location, airflow, light or another environmental factor may be competing with the intended explanation.

Model Limit: Conditions Can Interact

The Primary model treats important conditions one at a time so a simple relationship can be interpreted clearly. In real systems, factors can interact: the effect of one condition may depend on the level of another. Formal multi-factor experimental design belongs to later study. The Primary responsibility is to recognise that control simplifies reality rather than capturing every interaction at once.

Changed-Problem Transfer

Two covered cups are used to compare which material keeps water warm longer. The metal cup starts at 75°C beside an open window; the plastic cup starts at 65°C in a still corner. Identify the relevant competing conditions, distinguish them from irrelevant details, redesign the comparison, and propose one position-swap or repeat check that would strengthen the evidence.

RFE Check: What Should Survive After the Page Is Closed?

The durable routine is: What else could cause the same outcome? Did that condition differ? Can I keep it comparable, monitor it, swap it, repeat it or state it as a limitation? Control exists to protect meaning, not to decorate a method with a long list of constants.

Teaching Guide — Use This Last

For parents, tutors and teachers: begin with one deliberately confounded comparison. Ask the learner to justify each condition they want to control and reject irrelevant ones. Then use a position-swap example so the learner sees that hidden environmental differences can travel with location. Stop helping when the child can independently identify a plausible competing cause, decide how to control or check it, and state what limitation remains.

Explore the connected learning guides

Choose the question that brought you here. Open one useful guide, try a small task, and stop when you have what you need.

Take one question further

The same learning habit can travel across subjects, while each subject keeps its own methods. These routes help you notice a difficulty, understand one part of it, and return to something you can do.

A word is familiar, but using it is difficult.

Move from recognising a word to retrieving it in a new context. Understand vocabulary plateaus.

Try it without the guide: Choose one word you already know. Close the guide and use it in a new sentence. Explain why it fits; try another context tomorrow.

A piece of writing has ideas, but the reader loses the thread.

Make the order of events and the links between sentences clear. Explore composition writing.

Try it without the guide: Choose one short paragraph. Read the relevant explanation, close it, and revise the paragraph. Ask someone to tell you what happened and why.

The Mathematics seems familiar, but marks still disappear.

Find the first point where the working stops being reliable. Find Secondary 4 A-Math mark leakage.

Try it without the guide: For a Secondary 4 A-Math question you have attempted, locate the first uncertain line. Repair that step, then try a comparable question without the worked answer.

A Science fact is remembered, but the explanation is incomplete.

Connect the evidence to a scientific idea and the resulting change. Follow the Primary Science learning route.

Try it without the guide: Choose a familiar Primary Science example. Explain the evidence, the idea and the result without notes. Then change one condition and explain your prediction.

Two accounts of the world seem to disagree.

Check the question, source, date and evidence before combining claims. Explore the World Knowledge research library.

Try it without the guide: Take one claim. Find the source best placed to support it, note its date, and state what remains uncertain. Return to your original question.

There is plenty of help, but independence is hard to see.

Check what the learner can understand and do after support is removed. Understand how education works.

Try it without the guide: Choose one small task the child has practised. Agree on a calm, brief attempt without prompts. Use what happens to choose one next step, then stop.

For the structure behind these connections, read the eduKateSingapore runtime manifest and the eduKate ecosystem boot contract. The reader map describes public navigation; those manifests preserve the wider ownership and return rules.