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A1.1 · Form scientific questions, predictions, and testable hypotheses

Learn to form scientific questions, predictions, and testable hypotheses through clear examples and targeted practice.

Ontario Grade 11 Chemistry

Scientific Investigation Skills and Career Exploration

Asking useful scientific questions and making predictions in chemistry

A scientific investigation often begins with something you notice. A solid may seem to disappear when mixed with water, or a sample may look different after being left out. An observation is not yet an explanation. In this lesson, you will practise turning an observation into a question that can be investigated, then making a prediction and forming a testable hypothesis. These skills help you plan how to gather evidence without claiming results before an investigation is done.

What you will learn

1. Start with an observation, then ask a focused question

An observation is information gathered using the senses or a measuring tool. For example, you might observe that a spoonful of a solid is no longer visible after it is stirred into water. This describes what you noticed. It does not, by itself, tell you why it happened.
A scientific question asks about something that can be investigated using observations or measurements. A useful question is focused: it identifies what you will change and what you will look for. For example, “Does the amount of water affect the amount of salt that can dissolve?” can guide an investigation more clearly than “What happens to salt?”
Before writing a question, briefly review variables. A variable is a factor that can change. The independent variable is the factor deliberately changed. The dependent variable is the outcome observed or measured. In this example, the amount of water is the independent variable. The amount of salt dissolved is the dependent variable.
A fair investigation also keeps relevant conditions consistent. These are controlled variables. For the salt-and-water question, possible conditions to keep the same include water temperature, the kind of salt, and the mixing method. Naming these conditions helps make the question precise and the evidence easier to interpret.

2. Make a prediction and form a testable hypothesis

A prediction states what you expect to observe. It should connect to the question and name the expected direction or pattern when possible. For example: “If the amount of water is increased, then a greater amount of salt will dissolve before undissolved salt remains.” This is an expectation, not a report of evidence.
A hypothesis is a proposed explanation that can be checked with evidence. A useful format is “If [changed factor], then [expected outcome], because [reason].” The “if” part names the independent variable, the “then” part gives the predicted outcome, and the “because” part offers a reason that can be considered against observations.
For the salt example, a hypothesis could be: “If the amount of water is increased while other conditions stay the same, then more salt will dissolve, because a larger amount of water provides more water particles to interact with the salt particles.” This is a course-level particle model used to support a proposed explanation. It does not claim that an investigation has been completed.
A hypothesis is testable when an investigation can produce evidence that may support it or show that it needs revision. The outcome must be observable or measurable, and the conditions must be clear enough for someone to plan a fair comparison. A statement such as “Salt dissolves because it wants to” is not a useful scientific hypothesis: it gives no testable reason and treats the material as if it had intentions.
A prediction and a hypothesis are related but not identical. The prediction says what you expect to happen. The hypothesis includes a proposed reason for that expectation. Neither one is a guarantee. Scientific ideas are checked against evidence.

3. Check whether a question and hypothesis can guide an investigation

Read the question and ask: Can I identify what will be changed? Can I identify what will be observed or measured? Can I keep other important conditions consistent? If a key part is missing, revise the wording before planning an investigation.
A broad question can often be improved by narrowing its scope. “What affects dissolving?” leaves many possible factors open. A more focused version asks about one factor, such as the amount of water, and one outcome, such as the amount of salt that dissolves under stated conditions. This makes it clearer what evidence would answer the question.
Avoid writing an expected result as if it were already known. “More salt dissolved in the larger amount of water” sounds like a completed finding. If no investigation has been conducted, write it as a prediction: “I predict that more salt will dissolve in the larger amount of water.” Keep proposals separate from observations.
Use precise, observable language. Words such as “better,” “stronger,” or “a lot” may be unclear unless you explain how they will be judged. A measurable outcome could be recorded as a mass, volume, count, or other suitable quantity. Choose a measure that matches the question; do not add measurements that do not help answer it.
A particle model can help explain why you expect a pattern, but it does not replace evidence. In the example, the idea that water particles interact with salt particles provides a possible reason. The investigation would still need observations or measurements to check the prediction. The model and the evidence have different roles.

4. Improve your scientific wording

When revising, check that the question does not ask several things at once. If you change the amount of water and the temperature together, you may not know which change is connected to the outcome. For a focused question, identify one main independent variable and decide which other conditions should remain consistent.
Check that the outcome can be observed or measured in a clear way. “How much salt dissolves?” is more useful when the investigation plan explains how that amount will be determined. At this stage, you are forming the question and hypothesis; you are not required to invent results or claim that a proposed test has already been carried out.
Finally, check the “because” part of a hypothesis. It should give a possible scientific reason, not repeat the prediction in different words. “More salt will dissolve because more salt will dissolve” gives no explanation. A particle-level reason can be more useful, as long as it stays at a level you can explain and is treated as a proposal to examine.
The quality of a question is not measured by how complicated it sounds. A short question can be strong if it is focused, answerable with evidence, and connected to a clear prediction and hypothesis.

Worked example

Build a question, prediction, and hypothesis

A student notices that salt is no longer visible after it is stirred into water. They want to investigate whether the amount of water is connected to how much salt dissolves. Write a focused scientific question, a prediction, and a testable hypothesis. Identify the variables and conditions to keep consistent.
  1. Separate the observation from the investigation
    The starting observation is that the salt is no longer visible after mixing. It does not establish how much salt dissolved or why. The investigation will focus on one possible factor: the amount of water.
  2. Write a focused question
    Name the factor to change and the outcome to observe. This question can guide a comparison: “Does the amount of water affect the amount of salt that dissolves before undissolved salt remains?”
  3. State the prediction
    A prediction gives the expected pattern without presenting it as a result. For example: “If the amount of water is increased, I predict that a greater amount of salt will dissolve before undissolved salt remains.”
  4. Form a testable hypothesis
    Add a possible reason to the expected outcome. The larger amount of water may provide more water particles to interact with salt particles. This is a proposed explanation that can be compared with evidence, not a claim that the result has already been observed.
  5. Identify variables and fair conditions
    The independent variable is the amount of water. The dependent variable is the amount of salt dissolved before undissolved salt remains. Keep the water temperature, type of salt, and mixing method consistent so the comparison focuses on the amount of water.
Answer: Question: Does the amount of water affect the amount of salt that dissolves before undissolved salt remains? Prediction: If the amount of water is increased, I predict that a greater amount of salt will dissolve before undissolved salt remains. Hypothesis: If the amount of water is increased while other conditions stay the same, then more salt will dissolve, because a larger amount of water provides more water particles to interact with salt particles.
Check: The question identifies a change and an outcome. The prediction states an expected pattern. The hypothesis adds a proposed reason. The example describes a plan only; it does not invent measurements or report completed evidence.

Common mistakes and how to avoid them

Treating an observation as proof of an explanation.
Correction: Describe what was noticed first. Then write a question and a hypothesis that can be checked with evidence.
Writing a prediction as though it were a completed result.
Correction: Use wording such as “I predict” or “I expect” until evidence has actually been collected.
Changing several factors at once without a reason.
Correction: Choose one main factor to change and keep relevant conditions consistent so the comparison is easier to interpret.
Calling any opinion a testable hypothesis.
Correction: State an expected outcome and a proposed reason that can be examined using observable or measurable evidence.
Using a “because” statement that only repeats the prediction.
Correction: Give a possible scientific reason, such as a simple particle-level explanation, rather than restating the expected result.

Lesson summary

Check your understanding

Question 1

Which statement is a focused scientific question?
  1. Why is salt interesting?
  2. Does the amount of water affect the amount of salt that dissolves?
  3. Salt disappeared because the water was good.
  4. How can salt be made better?
Show answer and explanation
Does the amount of water affect the amount of salt that dissolves?
It identifies a factor that can be changed and an outcome that can be observed. The other statements are vague or do not clearly describe a testable relationship.

Question 2

What makes a prediction different from a hypothesis?
  1. A prediction gives an expected result; a hypothesis also proposes a reason.
  2. A prediction is always proven; a hypothesis is only a question.
  3. A hypothesis reports measurements; a prediction gives the procedure.
  4. There is no difference between them.
Show answer and explanation
A prediction gives an expected result; a hypothesis also proposes a reason.
A prediction states what you expect to observe. A hypothesis connects an expected outcome with a proposed explanation that can be examined.

Question 3

A student asks whether water temperature affects how much salt dissolves. Which could be a controlled condition in a fair comparison?
  1. The water temperature
  2. The amount of salt dissolved
  3. The type of salt used
  4. The prediction
Show answer and explanation
The type of salt used
The type of salt can be kept the same while temperature is changed. The outcome is what is observed, and the prediction is not an experimental condition.

Key terms

Observation
Information noticed using the senses or gathered with a measuring tool.
Scientific question
A focused question that can be investigated using observations or measurements.
Variable
A factor in an investigation that can change.
Independent variable
The factor deliberately changed in an investigation.
Dependent variable
The outcome observed or measured in response to a change.
Controlled variable
A condition kept consistent to make a comparison fair.
Prediction
A statement of what is expected to be observed or measured.
Hypothesis
A proposed explanation that includes an expected outcome and can be checked with evidence.

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Published by DoAssignment. This AI-assisted lesson follows Ontario Grade 11 Chemistry (SCH3U), expectation A1.1. 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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