Week 1 Biology Lab & Inquiry: Drops on a Penny

Part 1 — The Big Picture

This week you learned that biologists decide what is true by changing one thing, holding everything else steady, and letting the evidence speak. In this lab you run that kind of test yourself at a kitchen counter. You write a hypothesis before you start, count how many drops of plain water and of soapy water a penny holds, summarize your trials with an average and a range, and decide what your evidence supports. Then you check a chatbot's account of your experiment and catch where it mislabels the parts, scrambles the steps, or invents a number.

Time budget: Plan for about 120 minutes.

Part 2 — The Task

Guiding question: Does adding soap to water change how many drops a penny holds before the water spills, and what does your evidence allow you to claim?

Before you begin — hypothesis: Before you add a single drop, write your hypothesis in the if… then… because… form: if soap is added to the water, then the penny will hold more, fewer, or the same number of drops, because of a reason you can state. Then write the prediction your hypothesis makes for the two averages.

Workshop data: Your own penny drop counts, or the illustrative fallback counts

Source: Six drop counts you collect yourself at a kitchen counter with the procedure in Part 3; if you cannot run the protocol, use the six illustrative fallback counts printed in the fallback, which were constructed for this lab and are not real data.

• Rows: 6 trials, 3 with plain water and 3 with soapy water, shown as 2 rows of the data table (one row per condition); the first scaffold table has 7 rows that name the parts of the experiment rather than data
• Columns: condition, three trial counts in drops, sum, average, and range
• Unit: drops of water held on one penny before the water spills over the edge

Part 3 — Materials & Procedure

Tools and materials

• Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet)
• A penny, a dropper or a drinking straw, two cups, tap water, dish soap, and a paper towel
• A document or notebook for your written answers

Ways of working

• virtual-simulation-inquiry
• at-home-protocol-and-data-table
• figure-and-diagram-interpretation

Procedure

1. Set a clean, dry penny face up on a folded paper towel on a level counter. Fill one cup with plain tap water. Fill the second cup with tap water, stir in two drops of dish soap, and label the cups plain and soapy. Tool: A penny, a dropper or a drinking straw, two cups, tap water, dish soap, and a paper towel. Check: Two labeled cups and a dry penny that sits flat.
2. Before any drops go on the penny, write your hypothesis and prediction in the first table in Part 4, and fill in the independent variable, dependent variable, controlled variables, and control group. Tool: A document or notebook for your written answers. Check: The first table has a hypothesis in if… then… because… form and every part of the experiment named.
3. Plain water first: fill the dropper from the plain cup, hold it at the same height above the penny each time, and add drops one at a time, counting aloud, until the dome spills over the edge. Record the last drop that stayed on as the trial count, dry the penny, and repeat for three trials. Tool: A penny, a dropper or a drinking straw, two cups, tap water, dish soap, and a paper towel. Check: Three plain-water counts in the data table, each from a dry penny.
4. Rinse and dry the dropper and the penny so no plain water mixes in, then run three trials with the soapy cup the same way, at the same height, recording each count. Tool: A penny, a dropper or a drinking straw, two cups, tap water, dish soap, and a paper towel. Check: Three soapy-water counts in the data table, collected after the plain-water trials so soap never touches a plain trial.
5. Open a blank sheet. Type the three plain-water counts into cells B2, C2, and D2 and the three soapy counts into B3, C3, and D3. In E2 type =SUM(B2:D2), in F2 type =AVERAGE(B2:D2), in G2 type =MAX(B2:D2)-MIN(B2:D2), then copy E2 through G2 down to row 3. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: Each average equals its row's sum divided by 3, matching your hand calculation in the data table.
6. Complete the comparison table, answer the analysis questions in your document, then paste your completed tables into an approved chatbot with the prompt in Part 6 and check its answer against the scripted checks. Tool: A document or notebook for your written answers. Check: Three completed tables, written answers, and a list of the chatbot's errors with corrections.

Fallback route

When to use it: Use this route if you cannot get a penny, a dropper or straw, or dish soap, or if you cannot run the trials at home.

Use the six illustrative fallback counts below, constructed for this lab and not real data, as your data table, then complete every scaffold table, analysis question, and the critique step from them and submit the same items for equal credit.

This route earns the same credit as the primary route.

Six illustrative fallback counts, constructed for this lab, that stand in for your own trials.

Fallback model data

Condition	Trial 1 (drops)	Trial 2 (drops)	Trial 3 (drops)	Sum of the three trials	Average (sum ÷ 3)	Range (largest − smallest)
Plain water	41	44	47
Soapy water	19	22	25

Part 4 — The Scaffold

Name every part of the experiment before you collect data, so the test is fair from the first drop.

Student scaffold table 1

Part of the experiment	Your answer
Hypothesis (if… then… because…)
Prediction for the two averages
Independent variable
Dependent variable
Controlled variables (at least three)
Control group
One possible confound you will keep out

Record each trial as you go, then add the trials, divide by 3, and subtract the smallest from the largest.

Student scaffold table 2

Condition	Trial 1 (drops)	Trial 2 (drops)	Trial 3 (drops)	Sum of the three trials	Average (sum ÷ 3)	Range (largest − smallest)
Plain water
Soapy water

Compare the two conditions against the control, writing each step so a reader can check it.

Student scaffold table 3

Comparison	Your arithmetic	Result in words
Difference: plain average − soapy average
Reduction: difference ÷ plain average, as a percent
Spread inside each condition versus the gap between the averages

Part 5 — Analysis Questions

1. Using your data table, compute the difference between the two averages and then the reduction as a share of the plain-water average. Show every addition, division, and subtraction.
2. Picture your data as a bar chart: six bars, three for plain water and three for soapy water, with a line across each group at its average. Describe in words how tall each group's bars are, how far apart the two average lines sit, and whether the spread inside each group is smaller or larger than that gap.
3. Does your evidence support or fail to support your hypothesis? Write one conclusion sentence that uses supports or fails to support rather than proves, and name one result that would have counted against your hypothesis.
4. Explain which group is the control group and why your reduction is measured against its average rather than the soapy average. Then say in one sentence what about water this lab previews for next week.
5. Choose one and answer it in 3–4 sentences. (a) Name one confound that could have crept into your own setup, such as a changing drop height or a damp penny, and say how you would keep it out next time. (b) Explain why the lab uses three trials per condition, and say whether running more trials would change what you can claim.

Part 6 — AI-Critique Moment

Choose one equal-credit critique route. Route A: ask an approved AI tool to critique your completed work, then check its response against your own evidence. Route B is the no-AI equivalent printed below.

Approved tools: Claude, Gemini, ChatGPT, Grok, Microsoft Copilot.

Prompt to paste:

I've pasted my completed Week 1 Biology Lab & Inquiry tables above. I filled a penny with water one drop at a time until it spilled, three trials with plain water and three with water that had a little dish soap stirred in, using the same penny, dropper, and drop height. Please do six things. First, compute the average and the range for each condition from my tables, showing the arithmetic. Second, name the independent variable, the dependent variable, and the control group. Third, list the steps of the scientific method I followed, in order. Fourth, explain why soap changed the drop count and say whether my results prove that. Fifth, give any measured value for how much soap lowers water's surface tension, with its source. Sixth, as a stretch question for later in the course, say how many cells a body cell makes when it divides for growth, and what phenotype ratio a cross of two Tt parents gives.

Test the response for these likely failures:

• Chatbots often list the steps out of order, putting the experiment before the hypothesis or the conclusion before the analysis, or they drop the prediction entirely.
• Chatbots often mislabel the parts of the experiment: they call the drop count the independent variable, swap the two variables, or call the soapy cup the control group because it is the one being tested.
• Chatbots often say soap makes water lighter or thinner, or that the results prove soap lowers the drop count.
• Asked for a measured value, chatbots often invent a precise percentage drop in surface tension or a study that was never given, or quietly change one of my trial counts while averaging.
• Asked the stretch question, chatbots sometimes say a dividing body cell makes four cells or makes cells that differ from each other.
• Asked the stretch question, chatbots sometimes give the phenotype ratio of a Tt by Tt cross as 1:2:1.

Write 3–5 sentences naming one thing the chatbot got right and at least two places it went wrong or overreached, quoting its words and correcting each with evidence from your own tables or this week's chapter; mark the stretch answers as ones to check later.

Equivalent route (no AI required)

No AI account is required for this lab. Instead of the chatbot, critique this flawed analysis, printed here in full: "In my penny lab, plain water averaged 44 drops and soapy water averaged 22 drops, so my results prove that soap makes water lighter. The independent variable was the drop count, the dependent variable was the type of water, and the soapy cup was my control group because it was the one I was testing. I ran the experiment first, then wrote my hypothesis, then thought of my question. Soap cuts surface tension by 72 percent, as a study showed. As a preview of later weeks, a body cell dividing for growth makes four identical cells, and a cross of two Tt parents gives a 1:2:1 phenotype ratio." Mark it up: quote each flawed sentence, name what is wrong (an overclaimed or oversimplified mechanism, swapped variables or a mislabeled control group, the steps of the scientific method out of order, an invented figure, or a preview fact stated wrong), cite the evidence from your tables or this week's chapter, and write a corrected sentence beneath it; for the two preview sentences, say which later week will check them. This route assesses the same objective (Objective 1 — describe the practice of science in biology — the characteristics of life as a set, the levels of biological organization, the scientific method and a controlled experiment's variables and control, and the difference between a hypothesis and a theory — and explain evolution by natural selection as the unifying framework of biology) as the chatbot critique, takes comparable effort (about 30 minutes and 200–300 words), is scored by the same scoring criteria for the same credit, and its own submission artifact is the marked-up flawed analysis, posted in place of the chatbot share link and report.

Part 7 — What to Submit

• All three completed scaffold tables, filled from your own trials or the illustrative fallback counts
• Written answers to all five analysis questions
• The chatbot critique report with its share link, or the equivalent route's marked-up flawed analysis

Deliverable:

A short Biology Lab & Inquiry report on the drops on a penny test: three completed tables (the named parts of the experiment, the six trial counts with sums, averages, and ranges, and the comparison against the control), written answers to five analysis questions, and a critique of a chatbot's account of your experiment, or, on the equivalent route, a marked-up correction of the printed flawed analysis. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text. Choose a written, recorded, or visual form for your answers; every form is graded by the same scoring criteria.

Rubric

The rubric below shows how each submitted part is evaluated; bands are full, partial, or none.

Workshop evaluation criteria

Criterion	Full	Partial	None
Testable hypothesis and the parts of the experiment	A falsifiable if… then… because… hypothesis and a prediction appear before the data, and the independent variable, dependent variable, at least three controlled variables, the control group, and a confound are each named correctly.	A hypothesis appears but is not falsifiable or lacks a prediction, or one or two parts of the experiment are missing or swapped.	No hypothesis, or the parts of the experiment are not named.
Completed data table with correct arithmetic	All six counts are recorded from the student's own trials or the fallback counts, and every sum, average, and range is correct with the steps visible.	The table is filled, but one or two sums, averages, or ranges are wrong or their steps are missing.	No data are recorded, or the numbers are invented rather than collected or taken from the fallback.
Analysis in words	Questions 1 to 4 are answered accurately: the difference and the reduction against the control with steps, a word description of the bars, a conclusion that uses supports or fails to support with a disconfirming result, and the control group's role explained.	The questions are attempted, but one or two answers divide by the wrong baseline, claim the data prove the hypothesis, or blur the control group.	The analysis questions are missing or do not address the data.
Critique of the chatbot or of the printed flawed analysis	On either route, at least two errors are quoted and corrected with evidence from the student's own tables or the chapter, stretch answers are marked to check later, and one correct point is acknowledged; both routes earn this band equally.	On either route, errors are named but corrected without evidence, or only one error is caught.	No critique appears, or pasted output is submitted without any checking.
Reflection on the design of the test	The chosen reflection option is answered in 3–4 sentences that tie a specific confound or the number of trials to a concrete change in the test or in what can be claimed.	The reflection is answered but stays general or names no specific change.	No reflection is submitted.

Quality Gate

• Every count in the data table comes from your own trials or the printed fallback counts, never from memory or a chatbot.
• Each average equals its row's sum divided by 3, and each range equals the largest trial minus the smallest.
• The hypothesis was written before the first drop and has the if… then… because… form.
• The independent variable, dependent variable, controlled variables, and control group are each named, with plain water as the control group.
• No measurement, study, or source is invented anywhere in the submission.
• The critique quotes the chatbot or the flawed analysis and corrects at least two errors with evidence from your tables or the chapter.