Lesson plan Grade 2 Engineering & Design
Sparrowfield's Fish Tank Water Line: A Cover Design Lesson
A two-session grade 2 lesson in which students design jar covers that slow evaporation, test three setups, and argue which cover the class fish tank needs.
Objectives
- Students will explain that water leaves an open tank by moving into the air as vapor.
- Students will sketch and label a tank cover, showing how its shape keeps water above the surface.
- Students will write one opinion sentence naming a cover and giving a reason from the jar data.
Vocabulary
Key words: evaporate, vapor, cover, surface, design
Teacher overview
The second-grade room at Sparrowfield Elementary keeps two goldfish, and every few weeks a student has to top the tank back up because the water line has dropped below the filter outlet. The fish are not drinking it, and nothing is leaking. This lesson asks students to figure out where the water goes and then to design a cover that slows the loss without sealing the fish away from the air. Testing happens in three jars rather than in the tank itself, which keeps the fish undisturbed and gives the class a fair comparison. Plan for the vocabulary as well as the setup. Students often describe the water as having dried up, a phrase that hides the idea that the water moved into the room as invisible vapor, so repeat the word evaporate whenever a student says dried up.
Procedure
Session 1, opening (5 min). Show the tank, or a photograph of one, with a strip of tape marking where the water line used to sit. Read aloud: "No one spilled it. The fish did not drink it. The tank does not leak. So where did the water go?" Take four answers and circle any that mention the air.
Session 1, defining the problem (8 min). Ask what the top of the tank is open to. Guide the class toward a shared problem sentence, which is that the water surface is open to the room, so water leaves the surface and moves into the air. Write the sentence on chart paper and keep it posted for session 2. Name the constraint now: a cover that seals the tank completely also cuts off the air the fish need, so every design must let air through.
Session 1, sketching (10 min). Each student sketches one cover for the tank and labels three things: what it is made of, where the air gets in, and how the shape keeps water vapor above the surface. This is the formative check. Any sketch missing the labeled air opening goes back to the student before building begins.
Session 1, setting up the test (12 min). Groups fill three identical jars with the same amount of water, 8 ounces measured in the measuring cup, and label them. Jar A stays open. Jar B gets a flat plastic wrap lid with three pencil holes. Jar C gets a paper plate propped on craft sticks so it domes over the opening with a gap at each side. All three jars go in the same warm spot.
Session 2, measuring and opinion writing (20 min). One week later, pour the water from each jar back into the measuring cup and record the ounces. Students complete the handout and write their opinion sentence. Close by reading three sentences aloud and taking a class vote on the cover to build for the real tank.
Student Handout
Our jar data. Write the ounces of water poured into each jar and the ounces left after one week.
| Jar | Cover | Ounces poured in | Ounces left after one week |
|---|---|---|---|
| A | no cover | ||
| B | flat plastic wrap lid | ||
| C | paper plate dome |
- Which jar had no cover on it?
- Look at your three numbers. Which jar had the most water left?
- Where does the water go when it leaves an open jar?
- Every cover has a hole or a gap in it. Why do the fish need that opening?
- Draw your cover from the side. Label what it is made of and where the air gets in.
- Which cover should the class put on the fish tank? Write one sentence. Use the word because and one number from your data.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Answer: Jar A. Jar A is the open jar with no cover, which makes it the setup the other two are measured against.
- Answer: Accept the jar that matches the class's own recorded numbers. Most classes find Jar B, the plastic wrap lid with small holes, holds the most water because little vapor can escape through the small holes, with Jar C second and Jar A last.
- Answer: It moves into the air. Accept "it evaporates," "it turns into vapor," or "it goes into the room," and treat "it dried up" as partly correct until the student names the air.
- Answer: The opening lets air reach the water and the fish. Accept any answer noting that a sealed lid would trap the fish without fresh air, or that fish need air that comes through the water surface.
- Answer: Accept any side-view drawing showing a cover above the water with a labeled material such as plastic wrap or a paper plate, and with at least one labeled hole or side gap.
- Answer: Accept either Jar B's cover or Jar C's cover as long as the sentence names one cover, uses because, and cites a number the class recorded, for example "We should use the dome because it had 7 ounces left and the open jar had 6 ounces left."
Differentiation
Support
Run the three jars as one teacher-led demonstration rather than in groups, and give these students a two-column recording sheet with "poured in" and "left after" already printed. Accept a labeled drawing in place of written sentences for handout items 3 and 4, and read item 6 aloud.
Extension
Ask these students to add a fourth jar with a cover of their own design, write a prediction naming where its result will fall against Jars A, B, and C, and then explain after the test whether the prediction held and which feature of the design accounts for the result.
ELL supports
Pre-teach evaporate, vapor, cover, and surface with gestures and a labeled cross-section of a jar kept on the board. Provide the opinion frame "I think the ___ cover is better because ___," and let students rehearse the sentence with a partner before writing it.
Extensions
Put a strip of tape on the real tank at the current water line and check it once a week for a month so the class can watch the same loss happen slowly at full size. Students can then write a short set of tank care instructions, including when to top the water up, and tape it beside the tank stand.