Classroom activity Grade 4 Health & Consumer Science
Two-Minute Tap Test at Abernathy School: A Fair-Test Rotation
A grade 4 hands-on rotation comparing two toothbrushing habits by catching and measuring the water each one uses over the same two minutes.
Objectives
- Students will plan a fair test that changes only the rinse method between two trials.
- Students will measure and record in milliliters the water each method uses in two minutes.
- Students will name the failure points that could make a trial unfair and say how to prevent them.
Vocabulary
Key words: fair test, trial, milliliter, variable
Teacher overview
This rotation turns a familiar bathroom habit into a controlled comparison. Groups of four run two trials of dry toothbrushing over a dishpan, one with the tap running for the full two minutes and one with the tap off until a single cup rinse at the end, then measure what they caught with a marked pitcher. The comparison is built so that the timer, the faucet setting, and the basin stay the same in both trials, which leaves the rinse method as the only thing that can explain a difference in the reading. No answer key is provided, since every class measures its own faucet.
Activity Directions
- Set up before class. Place the dishpan in the sink under the faucet, turn the handle to a normal brushing flow, and mark that handle position with a strip of masking tape so it can be returned to exactly the same spot. Each group needs its own sink or spigot set up this way, since groups at one shared tap cannot finish two pairs of trials in the time below; with only one tap, have each group run one pair and pool the class data. Fill a stack of paper cups. Lay towels within reach. Print one handout per student.
- Introduce the question in one sentence: two people brush for the same two minutes, one leaves the tap running and one turns it off, and the class will measure the difference between the two methods. Ask for predictions and record two or three on the board without comment.
- Teach the fair-test rule before any water runs. Everything must stay the same in both trials except the rinse method. Have the class name what must be held constant, and steer the list toward the faucet handle position, the two-minute timer, the same dishpan, the same pitcher, and the same person brushing.
- Assign the four roles inside each group and post them: the Brusher, who brushes with a dry brush over the dishpan; the Timekeeper, who runs the two-minute timer; the Faucet Handler, who moves the handle only to the taped mark; and the Recorder, who writes the reading on the handout.
- Run Trial A. The Faucet Handler opens the tap to the mark, the Timekeeper starts two minutes, and the Brusher brushes over the dishpan the whole time with the water running. At two minutes, close the tap. Two minutes of running water is several liters, so scoop the caught water out of the dishpan with the pitcher one full liter at a time, count the full pitchers, and add the milliliters in the last partial pitcher. Empty the pitcher and dry the pan.
- Run Trial B with everything the same except the rinse. The tap stays off for the full two minutes of brushing. At the end, the Brusher rinses using one paper cup of water poured over the brush into the dishpan. Pour the caught water into the pitcher, read the milliliters, and record.
- Rotate the four roles and run both trials again so each group collects at least two pairs of readings. Groups that finish early run a third pair rather than adding a new variable.
- Stop the water work when every group has two complete pairs of readings, which usually takes about 30 minutes including setup and drying.
- Debrief for eight minutes. Ask each group to report its two Trial A readings and its two Trial B readings, and write them on the board in four columns. Expect Trial A readings to be considerably larger and to vary more between trials than Trial B readings, since a running tap depends on the handle position while a cup rinse is a fixed amount. Ask what would have happened to the comparison if one group had nudged the handle past the tape, and close by asking which trial each student would want to repeat at home tomorrow morning.
Student Handout
Imagine you are testing two ways to brush your teeth. Fill in this sheet as your group works.
| What we recorded | Trial A, tap running | Trial B, tap off until one cup |
|---|---|---|
| Water caught, first time (mL) | ||
| Water caught, second time (mL) |
- Write the one thing that changed between Trial A and Trial B.
- Write three things your group kept the same in both trials.
- Which trial caught more water, and by about how many milliliters?
- Were your two Trial A readings close to each other, or far apart? Write what you noticed.
- Name one mistake that would make a trial unfair, and write how your group would prevent it.
- Suppose you brush twice a day. Write one or two sentences telling which method you would use and why, using a number from your table.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Differentiation
Support
Assign these students the Timekeeper or Faucet Handler role first so they take part fully before they are asked to read a scale, and pair them with a Recorder who reads the pitcher aloud. Provide a pitcher whose milliliter marks have been traced over with a marker, and pre-fill the first row of the table with a worked example from the teacher demonstration.
Extension
Ask groups to design and run a third trial that tests a different water-saving idea, such as filling one cup before brushing and using only that cup for the whole two minutes, while holding the timer and the basin constant. Groups should state in advance what they expect and then compare the result with their Trial B reading.
ELL supports
Post the four role names with a sketch beside each one and rehearse them as a class before the first trial. Provide a word bank containing "trial," "the same," "changed," "milliliter," and "caught," and give the frames "We changed ___" and "We kept ___ the same" for handout items 1 and 2. Allow oral answers to items 3 through 6 with a partner before writing.
Extensions
Send home a one-page family version: brush once with the tap running and once with the tap off, catching the water in a bowl in the sink each time, and bring back the two amounts in whatever unit the family's measuring cup uses. Because kitchen faucets and measuring cups differ from household to household, spend the follow-up discussion on why the class results and the home results do not match exactly, and what a scientist does about that.