Scientific Inquiry, Pedagogy, and Laboratory Safety
Domain 4 - Scientific Inquiry, Pedagogy, and Laboratory Safety combines experimental design, instructional decision-making, and the legal and ethical duties that come with running a secondary science lab.
Inquiry and data
- A hypothesis must be testable and falsifiable. Identify the independent (manipulated) variable, dependent (measured) variable, and controlled variables.
- The control group receives no treatment or a placebo; replication and adequate sample size support reliability, while validity means measuring what you claim to measure.
- Accuracy is closeness to the true value; precision is repeatability. Correlation alone never establishes causation.
Pedagogy
- The 5E model sequences instruction as Engage, Explore, Explain, Elaborate, Evaluate.
- NGSS organizes content into three dimensions: Science and Engineering Practices, Crosscutting Concepts, and Disciplinary Core Ideas.
- Inquiry ranges from structured (teacher supplies question and procedure) to open (students design the investigation). Formative assessment guides instruction; summative assessment evaluates it.
- Anticipate misconceptions: plant biomass comes mainly from CO2 and water, not soil; natural selection acts on existing variation, not on mutations an organism "needs."
Laboratory safety
- Required PPE includes splash goggles, apron, and gloves; know the SDS for each chemical and report every spill and injury.
- Dilute acid by adding acid slowly to water with stirring - never water to acid, because the exothermic reaction can spatter.
- Store acids apart from bases, flammables in an approved cabinet, and use a fume hood for volatile work.
- Sterilize with an autoclave at 121 °C and 15 psi for 15 minutes; place broken glass in a sharps container; know eyewash and shower locations. The teacher supervises continuously and models correct technique.
Worked example
A student tests whether light intensity affects Elodea photosynthesis by counting bubbles per minute at 20, 40, and 60 cm from a lamp. Distance is the independent variable and bubbles per minute the dependent variable; temperature, plant mass, and NaHCO3 concentration must be held constant. The flaw to catch: moving the lamp also changes heating, so use an LED or heat filter and allow equilibration between trials.
Traps that cost marks
- Calling the treatment group the "control."
- Using precision and accuracy interchangeably.
- Assuming any hands-on activity is automatically inquiry.
- Forgetting that safety supervision is a legal duty, not a courtesy.