A hands-on STEM companion to the Cargo Ship Rescue breakout. Turn the density idea from Lock 2 into a real engineering test — then improve your design like a marine engineer.
🎯 The problem (define)
The Port of Houston needs a barge that carries the most cargo without sinking. Using a single square of aluminum foil, design and build a barge hull that holds the greatest number of pennies before it sinks or takes on water. Then redesign to beat your own record.
Anchor question: How does the shape of your hull change its volume, and how does that change its overall density and how much cargo it can float?
🧰 Materials (per team of 2–4)
2 squares of aluminum foil, 15 cm × 15 cm (one per build round)
A tub, sink, or large bowl of water
~60 pennies (or metal washers) as "cargo"
Paper towels, a ruler, and this recording sheet
Optional: a small amount of tape
🔁 The engineering design process
Define the problem: carry the most pennies on a foil barge without sinking.
Imagine & brainstorm: sketch two hull ideas. Which spreads the mass over the most volume — a flat raft, or a hull with tall walls?
Plan: choose one design, measure your hull, and predict a penny count.
Create: build your barge from one foil square. Seal any gaps.
Test: float it, then add pennies one at a time, spread evenly, until it sinks. Record the last count that stayed afloat.
Improve: redesign with the second foil square to beat Round 1. Change one thing (wall height, width, penny placement) so you know what helped.
📊 Record your trials
Round
Hull sketch / one change made
Predicted pennies
Pennies held (afloat)
1
2
Math connection: find the difference between rounds, and if the class pools data, the mean pennies per design. Math.6 ratios & data; 6.2(B) analyze data for patterns.
🗣️ Explain it — Claim, Evidence, Reasoning (CER)
Claim — What hull shape carried the most cargo?
Evidence — What did your two trials show?
Reasoning — Use the words mass, volume, and density to explain why. (A wider, deeper hull holds more mass in more volume, so the barge's overall density stays below the water's — and it floats.)
🚢 STEM career highlight — Naval Architect / Marine Engineer. These engineers design ships, submarines, and offshore rigs so they float safely and carry cargo efficiently. They use the exact idea you just tested: shape the hull so the vessel's overall density stays below the water's. (Labor data: O*NET & the Texas Workforce Commission; 6.4(C) investigate STEM careers.)
🧩 Extend it: Add a "wave" by gently rocking the tub — connect back to Lock 3 (an extra sideways push makes the forces on the cargo unbalanced). Or hang a paperclip "crane" and talk through the energy transfers from Lock 1.
TEKS aligned to this challenge
6.6(D) density relative to fluids · 6.1(B) design solutions with engineering practices · 6.1(G) develop & use models · 6.2(D) evaluate engineering designs · 6.3(A–C) develop, communicate & argue explanations · 6.4(C) STEM careers. Cross-curricular: Math (volume, ratios, mean of trials), ELAR (CER writing). Aligned to, not reproduced from, the official TEKS — confirm before adoption.