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A1.5 · Conduct inquiries safely while controlling relevant variables

Learn to conduct inquiries safely while controlling relevant variables through clear examples and targeted practice.

Ontario Grade 11 Chemistry

Scientific Investigation Skills and Career Exploration

Planning investigations while controlling relevant variables

A chemistry investigation may involve visible changes such as a colour change, bubbles, or a solid forming. Observing a change is only one part of good science. The investigation must also protect people, reduce avoidable hazards, and use a fair method. In this lesson, an inquiry means a planned way to ask a question and gather observations or measurements. A variable is a condition that can change. You will practise choosing which variable to change, which to measure, and which to keep the same. Safety and fair testing are linked: a useful result is not worth an unsafe procedure.

What you will learn

1. Start with the question and the observable evidence

You already know from earlier science that an observation is information gathered with the senses or a measuring tool. A conclusion is an explanation based on observations. Keep them separate. “The liquid became cloudy” is an observation. “A new substance formed” is an interpretation that may need more evidence.
A useful inquiry begins with a focused question. The question should name a condition you can change and an outcome you can observe or measure. For example, a student might ask whether changing the amount of a safe classroom material changes the amount of visible solid produced in a teacher-approved activity. This is a planning example, not a report of results.
At the particle level, a visible change can reflect changes in how particles are arranged or distributed. The particles themselves are too small to see in a classroom investigation. Therefore, record what you can actually observe, such as colour, cloudiness, or a measured quantity. Do not claim a particle-level explanation unless the evidence and course knowledge support it.
Before planning, define the outcome clearly. If the result is “cloudiness,” agree on how it will be judged. If a measuring tool is used, state what reading will be recorded and in what units. A clear outcome makes it easier for another student to repeat the procedure.

2. Plan a fair test by controlling relevant variables

The independent variable is the condition deliberately changed by the investigator. The dependent variable is the outcome observed or measured. A controlled variable is a condition kept the same so it does not unfairly affect the comparison. These terms help explain the logic of a fair test.
Suppose the question asks whether changing the amount of one material affects an outcome. That amount is the independent variable. The defined outcome is the dependent variable. Other conditions that could affect the outcome may include the amounts of other materials, the container, the mixing method, the time allowed before observing, or the way the outcome is measured. These are possible controlled variables; which ones matter depends on the specific question.
Changing several conditions at once makes the result difficult to interpret. If the outcome differs, you cannot tell which change caused the difference. Instead, change the independent variable deliberately and keep relevant conditions the same. “Relevant” means that a condition could reasonably affect the outcome being studied.
A control condition is a comparison condition that does not receive the planned change, or receives a usual condition for comparison. A control is useful only when it helps answer the question. Not every inquiry needs a separate control condition. Do not confuse a control condition with controlled variables: the first is a comparison; the second is a set of conditions kept consistent.
Plan how observations will be recorded before starting. Use the same units and measuring approach for comparable trials. If repeating a trial is safe and practical, repeated observations can show whether a result is consistent. Do not discard an unusual result simply because it differs from what you expected. Record it and consider whether a procedural issue might explain it.

3. Make safety part of the procedure

A hazard is something that could cause harm. Risk is the chance that harm may occur under the planned conditions. A safety check identifies hazards and decides how to reduce risk before work begins. Follow the teacher’s instructions and the school’s safety rules; do not decide on your own that a chemical or procedure is harmless.
Read the activity instructions and chemical labels before handling materials. Identify the required protective equipment, such as safety goggles, and use it as directed. Tie back long hair, secure loose clothing, and keep the work area clear. Use only the amounts and equipment authorized for the activity. Never taste a chemical. Avoid touching or directly smelling materials unless the teacher gives a safe, specific instruction.
Know where to find safety equipment and what to do if there is a spill, broken glass, or contact with a material. Tell the teacher promptly about an accident or an unsafe condition. Do not clean up a chemical spill or handle broken glass unless instructed and trained to do so. Keep containers labelled and do not return unused material to its original container unless directed.
A safe procedure is one that follows approved directions and includes suitable precautions. If a proposed method seems unsafe, stop and ask the teacher before proceeding. Do not change quantities, combine materials, heat substances, or use equipment in a way that is not part of the approved procedure. Safety is not a step to add after planning; it shapes which inquiry can be carried out.

4. Carry out, record, and review the inquiry

Before starting, check that the procedure answers the question and that the variables are clear. Confirm which condition will change, what outcome will be recorded, and which relevant conditions will remain consistent. Check the safety directions and equipment. If the plan cannot be followed safely, revise it with the teacher before collecting evidence.
During the inquiry, follow the same planned steps for each comparison. Record observations at the time they occur. Include units whenever a numerical measurement is recorded. Use sensible precision: do not report more digits than the measuring tool supports. If a tool gives readings to the nearest millilitre, for example, do not write a much more precise volume as if it had been measured.
Afterward, compare the observations with the question. Ask whether the independent variable was the only planned condition changed, whether the outcome was measured consistently, and whether any unexpected event may have affected the result. These questions help judge the quality of the evidence. They do not prove that a result is correct or establish a cause by themselves.
A clear record lets another person understand what was done and what was observed. Include the question, the variable plan, the safety precautions, the steps followed, and the observations. State limitations honestly. If a condition was not controlled or a measurement was uncertain, explain how that may affect the interpretation rather than hiding it.

Worked example

Plan a safe, fair comparison

A class wants to investigate whether changing the amount of a teacher-approved solid affects the cloudiness observed when it is mixed with a liquid. No results have been collected. Plan the inquiry without claiming what the outcome will be.
  1. Focus the question
    Ask how the amount of the approved solid relates to the observed cloudiness. Define cloudiness before beginning, using a teacher-approved observation method or measuring tool. This makes the outcome more consistent between trials.
  2. Name the variables
    The amount of solid is the independent variable because it is deliberately changed. The cloudiness observation or measurement is the dependent variable because it is the outcome recorded. Keep the liquid amount, container type, mixing method, and observation time the same if they could affect the comparison.
  3. Add a safety plan
    Use only the material, quantities, and procedure approved by the teacher. Check the label and directions, wear the required protective equipment, and keep the work area clear. Ask the teacher about disposal and spill procedures before starting. Do not begin if any direction is unclear.
  4. Record evidence consistently
    Prepare a record with the amount used, the cloudiness observation or measurement, and any relevant notes for each planned trial. Use the same method and units each time. Record actual observations only after carrying out the approved procedure; do not predict them as if they were results.
  5. Review the plan
    Check that only the amount of solid is intentionally changed and that other relevant conditions remain consistent. If cloudiness differs, describe the evidence first. Then consider whether the procedure supports a comparison and identify any uncontrolled condition that could affect interpretation.
Answer: A suitable plan identifies the amount of solid as the independent variable and cloudiness as the dependent variable, keeps relevant conditions consistent, follows teacher-approved safety directions, and records observations without inventing results.
Check: The plan is fairer because the intended change is isolated from other relevant conditions. It is safe only if the teacher approves the materials and procedure and the required precautions are followed.

Common mistakes and how to avoid them

Changing more than one relevant condition and then attributing the outcome to only one change.
Correction: Change the independent variable deliberately and keep other relevant conditions consistent.
Calling every condition kept the same a control condition.
Correction: A controlled variable is kept consistent; a control condition is a comparison condition.
Writing an explanation as if it were a direct observation.
Correction: Record what was seen or measured first. Label interpretations as conclusions and support them with evidence.
Starting an activity before checking its instructions and hazards.
Correction: Review the approved procedure, safety directions, protective equipment, and response steps before beginning.
Changing an unexpected result to match what was expected.
Correction: Record the observation honestly and consider possible procedural limits when interpreting it.

Lesson summary

Check your understanding

Question 1

A student changes the amount of a material and records the resulting cloudiness. Which is the dependent variable?
  1. The amount deliberately changed
  2. The cloudiness recorded
  3. The container kept the same
  4. The safety goggles worn
Show answer and explanation
The cloudiness recorded
The dependent variable is the outcome observed or measured. Here, that outcome is cloudiness.

Question 2

Why should a student keep the mixing method the same in a comparison, if it could affect the outcome?
  1. So the mixing method becomes the independent variable
  2. So the comparison focuses on the planned change
  3. So no observations need to be recorded
  4. So the result is guaranteed to match the prediction
Show answer and explanation
So the comparison focuses on the planned change
Keeping a relevant condition consistent helps make the planned change the main difference between the comparisons. It does not guarantee a particular result.

Question 3

A student is unsure how to respond to a spill during an approved activity. What should the student do?
  1. Clean it up immediately without checking the procedure
  2. Continue the investigation and report it later
  3. Stop, keep clear as appropriate, and tell the teacher promptly
  4. Pour the material into another container
Show answer and explanation
Stop, keep clear as appropriate, and tell the teacher promptly
The student should follow school procedures and promptly alert the teacher. Untrained cleanup or transferring material can increase risk.

Key terms

Inquiry
A planned way to ask a question and gather observations or measurements.
Variable
A condition that can change in an investigation.
Independent variable
The condition deliberately changed by the investigator.
Dependent variable
The outcome observed or measured.
Controlled variable
A relevant condition kept consistent during a comparison.
Control condition
A comparison condition used to help answer an inquiry question.
Hazard
Something that could cause harm.
Risk
The chance that harm may occur under particular conditions.

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Published by DoAssignment. This AI-assisted lesson follows Ontario Grade 11 Chemistry (SCH3U), expectation A1.5. It is a study resource, not an official curriculum publication.

Before publication, the draft is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability, and then requires administrator approval. Errors can still occur, so corrections are welcomed.

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