Week 1 — Lab / Scientific Inquiry · "Drops on a Penny"

Course: Introduction to Biology — General Biology I (BIOL 101) · Silver Oak University (fictional sample) · Prof. Castellano
Objective: Objective 1 — design and run a controlled experiment; identify variables; collect and interpret data · SLO A (scientific reasoning)
Worth 50 points · Labs group = 15% of the grade · Lab 1
Format: a hands-on at-home controlled experiment (no special equipment) — you'll design it, run it, build a data table, and then catch the AI's mistakes when it interprets your results.

This is the course's signature weekly component. Every instructional week has one lab. This week's is a simple at-home protocol; later weeks use free virtual simulations (a virtual microscope, PhET, HHMI BioInteractive, LabXchange, Learn.Genetics). All lab resources are links to external sites — nothing to buy or download.

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Part 1 — The Big Picture

This week you learned the machinery of science: a testable hypothesis, an independent variable you change, a dependent variable you measure, controlled variables you hold constant, and a control group to compare against. Now you'll run a real experiment that uses every one of those pieces — and the result quietly previews next week's topic, the amazing properties of water.

The phenomenon: water molecules cling to each other (cohesion), so a surprising number of water drops will pile up into a dome on a penny before spilling. Dish soap breaks up that clinging (it lowers surface tension). Your job is to test, with data, whether soap changes how many drops a penny can hold.

Background (optional, ~5 min): Amoeba Sisters — "Properties of Water" (watch 1:35–3:00 on cohesion and surface tension): 🔗 https://www.youtube.com/watch?v=3jwAGWky98c

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Part 2 — Your Scientific Question & Hypothesis

The question: Does adding dish soap to water change how many drops a penny can hold before the water spills over?

Before you start, write your hypothesis (an "if… then…" statement is perfect):

If I add dish soap to the water, then a penny will hold __ (more / fewer) drops than with plain water, because ____.

Write it down now — you'll compare it to your results at the end. (A "wrong" prediction is completely fine; science is about testing, not guessing right.)

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Part 3 — Materials & Procedure

You need (all common household items):
- 1 penny (or any coin) · a small cup of plain water · a separate cup of water with a few drops of dish soap stirred in · a medicine dropper, pipette, or a drinking straw (dip and lift to release drops) · paper towels.

Procedure:
1. Put the penny on a flat, dry paper towel, heads up.
2. Plain water — Trial 1: add one drop at a time, counting, until the water spills over the edge. Record the number of drops before the spill. Dry the penny.
3. Repeat for Plain water — Trials 2 and 3 (dry the penny each time).
4. Soapy water — Trials 1, 2, 3: do the same three trials using the soapy water. Dry the penny between trials.
5. Hold these the same every trial (your controlled variables): the same penny, the same dropper, the same person dropping, the same drop height, the same room/table.

No household items handy? You can run an equivalent virtual experiment by varying a liquid's properties in a free simulation, or simply use the model data table in Part 8 to practice the analysis — but the at-home version takes ten minutes and is more fun.

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Part 4 — Data Table (fill this in)

Trial	Plain water — drops	Soapy water — drops
1	______	______
2	______	______
3	______	______
Average (mean)	______	______

Mean = (Trial 1 + Trial 2 + Trial 3) ÷ 3. Show your arithmetic.

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Part 5 — Identify Your Experiment's Parts

Answer in a sentence each:
1. Independent variable (what you changed): __
2. Dependent variable (what you measured): _
3. Two controlled variables (kept the same):
4. Control group (the baseline): ___

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Part 6 — Analysis Questions

1. Which water held more drops on average — plain or soapy? By about how many drops?
2. Explain the result using the idea of cohesion / surface tension. Why would soap reduce the number of drops?
3. Why did you run three trials for each instead of just one? What does taking the average protect you from?
4. Name one thing that could have gone wrong (a source of error) and how you'd improve the experiment next time.
5. Connect it: which characteristic of life or property of water does this experiment illustrate, and how does it relate to living cells (hint: water is the medium life runs in)?

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Part 7 — AI-Critique Moment (required — this is the BYOAI step)

Now bring in your approved chatbot (Gemini, Claude, or ChatGPT) and be the scientist who checks its work.

1. Paste your data table into the chatbot and ask it: "Interpret my results. Which liquid held more drops, what's the average for each, and what does this say about surface tension? Also tell me the independent and dependent variables."
2. Check everything it says against your own work:
   - Did it calculate the averages correctly? (Re-add the three trials and divide by 3 yourself.)
   - Did it correctly call the independent variable the water type and the dependent variable the drop count — or did it swap them? (Chatbots do this constantly.)
   - Did it get the science right — that soap lowers surface tension, so fewer drops — or did it reverse the cause?
3. Write 2–3 sentences reporting what the AI got right and at least one thing you had to correct or watch carefully. (If it happened to get everything right, say how you verified each claim — that's the skill.)

The habit all term: the tool drafts, you judge. A chatbot will confidently mis-add a column or flip your variables — catching it is the point.

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Part 8 — What to Submit

Submit a single document (or text entry) with: your hypothesis, your completed data table with the two averages, your Part 5 variable labels, your Part 6 answers, and your Part 7 AI-critique paragraph. Due Sunday, Sep 6, 11:59 p.m. (50 points).

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Instructor answer key & model data — REMOVE BEFORE PUBLISHING TO STUDENTS

Students collect their own numbers, so exact counts vary (plain water typically holds ~20–35 drops; soapy water far fewer). The model dataset below is for grading the analysis and arithmetic; all numbers are pre-computed and independently verified.

Model data table (illustrative, clean values):

Trial	Plain water	Soapy water
1	28	12
2	30	14
3	32	16
Mean	30	14

• Plain-water mean = (28 + 30 + 32) ÷ 3 = 90 ÷ 3 = 30 drops. ✓
• Soapy-water mean = (12 + 14 + 16) ÷ 3 = 42 ÷ 3 = 14 drops. ✓
• Difference = 30 − 14 = 16 drops more for plain water.
• Percent reduction from soap = (30 − 14) ÷ 30 = 16 ÷ 30 = 0.533… ≈ 53% fewer drops with soap. ✓

Expected answers:
- Part 5: (1) IV = type of water (plain vs. soapy); (2) DV = number of drops the penny holds; (3) two of: same penny, dropper, person, drop height, table; (4) control group = the plain-water trials (the baseline).
- Part 6: (1) Plain water holds more (by ~16 drops in the model). (2) Water's cohesion (hydrogen bonds pulling molecules together) creates high surface tension, which holds the dome together; soap molecules disrupt that bonding, lowering surface tension, so the dome collapses sooner → fewer drops. (3) Three trials + averaging reduces the effect of random error (a shaky drop, an early spill) and gives a more reliable, representative result. (4) Reasonable errors: inconsistent drop size, bumping the table, water already on the penny, miscounting — fix by standardizing the dropper and drying fully. (5) Illustrates a property of water (cohesion/surface tension) central to life because water is the solvent and medium inside every cell; cohesion also helps water move in plants (previews Week 2).
- Part 7 (AI-critique): full credit for a specific catch — most commonly the AI swapping IV and DV, mis-adding an average, or reversing the soap→surface-tension cause. Full credit also if the student verified each AI claim against their own arithmetic and reasoning.

Grading rubric — 50 points

Criterion	Full	Partial	None
Hypothesis — a clear, testable "if…then…" prediction with a reason (8)	8	4–6	0–2
Data table — three trials per condition + both means computed correctly (15)	15	8–12	0–6
Variables (Part 5) — IV, DV, two constants, and control group all correct (12)	12	6–10	0–4
Analysis (Part 6) — correct comparison + cohesion/surface-tension reasoning + why replicate/average (10)	10	5–8	0–4
AI-critique (Part 7) — names a specific thing checked/corrected in the AI's interpretation (5)	5	3	0–2

Quality gate (self-checked): every number in the model dataset is pre-computed and independently re-verified (means 30 and 14; difference 16; ~53% reduction); the science (soap lowers surface tension → fewer drops) is correct; variables map correctly (IV = water type, DV = drop count, control = plain water). No student-collected number is asserted as "the" answer — the key grades the analysis, not a specific count.