Classroom activity Grade 2 Engineering & Design
Crabapple Pond's Floating Boom: A Grade 2 Design Station
A 35-minute grade 2 station activity in which teams build floating booms from yarn, foil, and straws to corral floating litter in a tub and compare two designs.
Objectives
- Students will state the floating litter problem in one sentence using what they observed in the tub.
- Students will build a floating boom and test whether it holds litter back in moving water.
- Students will compare two of their own boom designs and name which one worked better and why.
Vocabulary
Key words: boom, float, litter, design, test
Teacher overview
After a storm, wrappers and leaves float across Crabapple Pond and collect against the far bank where the park crew cannot easily reach them. Crews handle this with a boom, which is a floating barrier strung across the water to hold drifting material in one place so it can be scooped out. In this station activity, teams of three build a boom from yarn, foil, and straws, test it in a tub while the teacher makes a slow current with a hand, rebuild it once, and compare the two versions. Litter rides on the surface of the water, so a boom that sinks holds nothing back, which makes buoyancy and an unbroken line across the water the two features a working design has to get right.
Activity Directions
Set up two tubs (before class). Fill each tub with about 3 inches of water and set it on a towel. Sprinkle a spoonful of pepper or a handful of paper dots on the surface of each. Set out the building materials at a third table, which becomes the supply station.
Observe the problem (5 min). Gather the class around one tub. Move your hand slowly through the water to make a current and let students watch the litter drift and pile at one end. Ask each team to name one thing they noticed. Teams write the problem in one sentence on their handout.
Assign teams and stations (3 min). Form teams of three with three jobs: builder, tester, and recorder. Two teams work at each tub and take turns testing. Teams not testing are at the supply station building or rebuilding.
Build round 1 (7 min). Each team takes materials from the supply station and builds a boom long enough to stretch across its tub. State the constraint out loud: the boom must float on its own, and the team may not hold it up during the test.
Test round 1 (5 min). The tester lays the boom across the tub. The teacher or a partner makes one slow current with a hand for ten seconds. Teams watch whether the litter stops at the boom, slips under it, or pushes it aside. The recorder writes one word: stopped, under, or pushed.
Rebuild and test round 2 (10 min). Each team changes one thing about its boom and tests again in the same way. Common changes are adding straws to make it float higher, taping the ends to the tub rim so it cannot swing, and making the line long enough to touch both sides.
Scoop and finish (2 min). After the second test, each team scoops the trapped litter out with a spoon and sets the boom on a towel. The activity ends when every team has completed two tests and recorded both results.
Debrief (3 min). Ask two questions and take three answers each: "What made litter slip past a boom?" and "Why does a boom have to float instead of sitting on the bottom?" Close by pointing out that a boom collects litter but does not remove it, which is why a crew still has to come scoop.
Student Handout
- Write the problem at Crabapple Pond in one sentence. Use what you saw in the tub.
- Draw your team's first boom from above. Label what it is made of.
- Which boom held back more litter, your first one or your second one?
- Why did some litter slip past your boom?
- Which boom would you use at a real pond? Give one reason.
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: Accept any sentence naming floating litter and the water that moves it, such as "Litter floats on the pond and the water pushes it to one side." A sentence that names only litter, with no water or movement, should be sent back for one more detail.
- Answer: Accept any labeled drawing showing a line stretched across the water with at least one named material, such as yarn, foil strips, straws, or craft sticks. Drawings that show the boom along the water instead of across it are worth a follow-up question about which way litter drifts.
- Answer: Accept whichever boom matches the team's own recorded results. Most teams find the second boom performs better because they added floats or closed the gap at the ends, and a team that found no change should be able to say what they altered.
- Answer: Accept any answer naming a gap, a sunken section, or a boom that swung aside. Strong answers say the litter went under a part that sank or through a space at the end of the line.
- Answer: Accept either boom as long as the reason refers to floating, to covering the whole width, or to holding steady in the current, for example "the second one, because the straws kept it on top of the water."
Differentiation
Support
Pre-cut yarn to tub width and pre-tape two straws to it so these teams begin with a floating base and change only one feature. Let them dictate the problem sentence in item 1 to an adult, and accept a drawing with single-word labels for the rest of the handout.
Extension
Give these teams a second constraint of a boom that must let water through while holding litter back, and ask them to explain in two sentences why a park crew would want that. Have them design a scooping tool from the same supply table and describe how it works with the boom.
ELL supports
Pre-teach float, sink, boom, and litter by dropping a straw and a coin into a clear cup and naming what each one does. Provide the frames "The litter went ___ my boom" and "My second boom was better because ___," and allow teams to point at their model while reporting to the class.
Extensions
Walk to a schoolyard drain or a curb after a rain and look, without touching the water, for the same pattern of material collecting where the water slows. The class can then design a poster showing what a boom does and what it does not do, and post it beside the classroom sink.