Guided Practice
Overview
Practice applying the scientific method to various scenarios. Work through designing experiments, identifying variables, and evaluating procedures.
Practice Problems
Question 1: A student wants to test if plants grow faster with music. What is the independent variable?
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Answer: The presence or type of music (what the experimenter changes)
The independent variable is what you manipulate to see its effect on the dependent variable.
Question 2: In the same plant experiment, what is the dependent variable?
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Answer: Plant growth (measured in height, mass, or leaves)
The dependent variable is what you measure - it "depends" on the independent variable.
Question 3: List three controlled variables (constants) for the plant-music experiment.
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Answer: Any three: type of plant, amount of water, amount of light, soil type, pot size, temperature, duration of experiment
Controlled variables must stay the same for all groups to ensure a fair test.
Question 4: Write a testable hypothesis for: "Does hand sanitizer kill more bacteria than soap?"
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Answer: "If hand sanitizer is used instead of soap, then fewer bacteria will remain on hands because sanitizer contains alcohol which kills bacteria on contact."
A good hypothesis has an if-then-because structure that is testable and includes reasoning.
Question 5: Why does an experiment need a control group?
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Answer: To provide a baseline for comparison and show what happens without the independent variable
Without a control, you can't tell if changes are due to your variable or other factors.
Question 6: A student tests one plant with fertilizer and one without. What's wrong with this design?
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Answer: Sample size is too small - need multiple plants in each group
One plant might naturally grow faster regardless of fertilizer. Multiple samples reduce individual variation.
Question 7: Identify the flaw: "I tested my hypothesis and proved it true."
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Answer: Science doesn't "prove" hypotheses - it supports or fails to support them
Evidence can support a hypothesis, but future tests might yield different results. Science stays open to revision.
Question 8: What makes an experiment "repeatable" and why does this matter?
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Answer: Clear procedures that others can follow to get similar results; this validates findings
If only one scientist gets certain results, they might have made an error. Replication builds confidence.
Question 9: Convert this question to a testable hypothesis: "Are expensive running shoes better?"
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Answer: "If runners wear $150 shoes vs. $50 shoes, then their mile time will improve because expensive shoes have better cushioning technology."
Made testable by defining "better" (mile time), specifying comparison (price levels), and being measurable.
Question 10: After an experiment, results don't support the hypothesis. Is the experiment a failure?
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Answer: No - negative results are still valuable scientific findings
Learning what doesn't work is important. The hypothesis was wrong, not the experiment. Revise and test again.