Designing a Scientific Investigation

Learning Objectives

• Follow the complete sequence of a scientific investigation:
  • Aim/Problem
  • Materials & Equipment
  • Method/Procedure
  • Results (including Data)
  • Conclusions
• Define, list, and explain each step in the scientific method
• Apply the scientific method to real or hypothetical experiments

Review of Physical Changes (Prior Knowledge Connection)

• Melting – solid → liquid (gain of heat)
• Condensation – gas → liquid (loss of heat)
• Sublimation – solid → gas (gain of heat, skips liquid)
• Freezing – liquid → solid (loss of heat)
• Evaporation – liquid → gas (gain of heat)
• Deposition – gas → solid (loss of heat, skips liquid)
• Essential reflection questions:
  • Which change is most common in everyday life?
  • Which ones involve gaining vs. losing heat energy?

Unlocking Content Vocabulary

• Investigation – systematic search for answers
• Problem – scientifically testable question
• Equipment – tools & supplies required
• Procedure – ordered, repeatable steps
• Data / Results – collected observations & measurements
• Conclusion – evidence-based explanation answering the problem

Scientific Investigation – Big Picture

• A logical, step-by-step approach scientists use to explain phenomena and answer questions about the natural world.
• Ensures repeatability, transparency, and evidence-based reasoning.

Step 1 – Aim / Problem

• Heart of the investigation.
• Qualities of a strong aim:
  • Clear & specific
  • Answerable via experiment
  • Measurable in some form (qualitative or quantitative)
• Example aims:
  • “Does the type of liquid affect how quickly an ice cube melts?”
  • “Does the amount of light affect bean-plant growth?”

Step 2 – Materials & Equipment

• Complete list of everything needed.
• Considerations:
  • Adequacy – nothing missing
  • Safety – non-hazardous choices when possible
  • Availability – realistically obtainable items
• Example list (ice-cube experiment):
  • Ice cubes, $3$ cups, water, soda, saltwater, timer

Step 3 – Method / Procedure

• Detailed recipe that anyone can follow and replicate.
• Must be:
  • Clear & concise
  • Sequential (logical order)
  • Repeatable (another person should obtain comparable results)
• Example skeleton (paper-towel absorbency):
  1. Cut equal-sized paper-towel squares.
  2. Pour $50\,\text{mL}$ water into a graduated cylinder.
  3. Dip square into water for $5$ s; let excess drip $10$ s.
  4. Record remaining water volume; calculate absorbed amount.
  5. Repeat for each brand $n=3$.

Step 4 – Data & Results

• Raw information gathered:
  • Observations (qualitative)
  • Measurements (quantitative)
• Presentation formats:
  • Tables, charts, graphs for trend visualization
• Sample data set (ice-cube experiment):
  • Water: $(10\ \text{min})$
  • Soda: $(12\ \text{min})$
  • Saltwater: $(8\ \text{min})$

Step 5 – Conclusion

• Interpret results; directly address original aim.
• Key attributes:
  • Evidence-based (no speculation beyond data)
  • Explanatory (why the result occurred)
  • Declarative (supports or rejects hypothesis)
• Sample conclusion: “Saltwater melted ice fastest, likely due to lower freezing point caused by dissolved ions.”

Hypothesis – Educated Guess

• Definition: Proposed explanation or prediction based on limited evidence that can be tested.
• Writing tips:
  1. Single, clear sentence.
  2. Must be testable.
  3. Use “If … then …” structure.
• Example bank:
  • “If plants receive more sunlight, then they will grow taller.”
  • “If plants are watered more frequently, then soil moisture will be higher.”
  • “If different fertilizers are used, then tomato yield will vary.”

Variables

• Independent Variable (IV) – factor you intentionally change.
• Dependent Variable (DV) – factor you measure; responds to IV.
• Controlled Variables (CVs) – kept constant to ensure a fair test.
• Visual aid (plant example):
  • IV: hours of sunlight $\rightarrow$ A $=2$ h, B $=4$ h, C $=6$ h
  • DV: plant height (cm)
  • CVs: species, pot size, soil, water volume

Worked & Practice Examples (Quick Reference)

1. Ice-cube liquids
   • IV: liquid type
   • DV: melt time
   • CVs: ice size, cup size, room temp
2. Bean-plant light
   • IV: light amount
   • DV: height after $15$ days
   • CVs: water $100\,\text{mL}$/2 days, pot, soil
3. Radish-soil types
   • IV: soil type (sandy, clay, loam)
   • DV: height after $2$ weeks
4. Screen-time vs. sleep
   • Hypothesis: “More screen time → poorer sleep quality.”
5. Ice-melting vs. room temp
   • Hypothesis: “Higher temperature → faster melting.”
6. Paper-towel absorbency (student design exercise)
   • Students to define IV (brand), DV (mL absorbed), CVs (square size, dip time, water temp)

Assessment-Style Multiple-Choice Review (with correct answers)

1. Purpose of defining the aim/problem: To identify the research question
2. Importance of listing materials & equipment: To organize materials and ensure the experiment can be replicated exactly (best overall answer C)
3. Purpose of the method/procedure: To outline clear steps of conducting the experiment
4. Typical data presentation: Tables, graphs, charts
5. Main purpose of the conclusion: Determine whether the hypothesis was supported by the results

Practical, Ethical & Philosophical Considerations

• Safety: choice of non-hazardous materials; PPE when required.
• Fair testing: control variables diligently; reduces bias.
• Reproducibility & transparency: detailed procedure + full material list.
• Environmental impact: minimal waste, proper disposal.
• Societal relevance: experiments (e.g., fertilizer efficacy) tie directly to agriculture & sustainability.

Key Takeaways

• Scientific investigations rely on a rigorous structure to yield trustworthy, reproducible knowledge.
• Clear hypotheses guide data collection; variables isolate cause-effect relationships.
• Robust conclusions emerge only when data are properly gathered, organized, and interpreted.
• Mastery of these steps equips learners to scrutinize information critically and design their own inquiries.