Bio 121 · CSLO 3 · Faculty Reference

Assessment Instrument — Answer Key & Rationale

The full 8-item scientific-method quiz, with correct answers and the reasoning behind each — so your Lab 6 wrap-up can target exactly what the items ask.

Format: 8 items · multiple choice Mastery: ≥ 4 of 8 = Meets Expectations Timing: ~15 min · you proctor
Faculty reference — keep it that way. This page shows the correct answers. It lives behind the faculty view and should not be shared with students or posted where students can reach it. Students see the questions only during the proctored quiz. (In the live quiz, answer options are shuffled per student, so "the first option" is not a giveaway.)
8
items
50%
mastery threshold
7
sub-skills
CATALASE
student passcode
Q1Hypothesis Formulation
Given that the pH inside potato cells (the origin of the catalase) is about 7, which of the following would be a good HYPOTHESIS?
Why

A hypothesis must be testable and predictive. Option A states an expected outcome based on known optimal pH. The others are questions, observations, or procedures.

Q2Experimental Design
You hypothesize that increasing the amount of enzyme (catalase) will speed up the reaction of turning H₂O₂ into water and oxygen. Which would be a good experiment?
Why

Valid experiments isolate one variable (catalase amount) while keeping others constant (H₂O₂ at 3ml). The other options vary irrelevant factors.

Q3Controls & Variables
You observe that adding 3ml of hydrogen peroxide to catalase at room temperature results in 24mm bubbles. You hypothesize that cold catalase (4 °C) will slow the reaction. Which would be the control and variable?
Why

The control is the known standard (room temp, the 24mm result). The variable is what you're testing (cold). Don't confuse controls with missing components.

Q4Drawing Conclusions
You hypothesize that boiling catalase will result in no bubbles. Tube 1 (room-temp catalase) = 32mm. Tube 2 (boiled catalase) = 0mm. Best conclusion?
Why

Conclusions state whether data "supports" the hypothesis — never "proves." 0mm matches the prediction of denaturation. (This is the "support vs. prove" distinction — a common student error.)

Q5Good Hypothesis Traits
A good hypothesis:
Why

The defining trait is testability. Hypotheses can be wrong, don't prove theories, and aren't questions.

Q6Observations vs. Interpretations
When you add catalase to hydrogen peroxide you see the formation of bubbles. This is a(n):
Why

Bubbles forming is a direct empirical observation — raw data before any analysis or interpretation.

Q7Making Predictions · priority
You hypothesize catalase works best at pH 7 to speed up the reaction. What prediction can you make?
Why

Predictions are specific expectations derived from the hypothesis. Deviation from optimal pH should reduce activity. This is a priority sub-skill this cycle — see the teaching guide for the hypothesis-vs-prediction distinction.

Q8Positive Controls · priority
Your lab book says adding catalase to hydrogen peroxide produces bubbles. Which would be the best positive control?
Why

Positive controls include all components known to produce the expected result, confirming the system works. This is a priority sub-skill this cycle — see the teaching guide for the positive-control-vs-experiment distinction students most often miss.

Two of these eight are this cycle's focus. Q7 (predictions) and Q8 (positive controls) are the sub-skills item analysis flagged as the remaining floor. When you review after Lab 6, weight your attention there — the teaching guide in your dashboard has concrete, research-backed moves for both. The instrument itself is unchanged from Runs 1 and 2, so results stay comparable across the cycle.