How Do Big Ships Float?
A coin sinks but a giant metal ship floats — solve the mystery with a foil boat of your own design.
⏱️ Micro Plan — 4 short parts · about 20 min in total
- 1The Question5 min
- 2Predict5 min
- 3Experiment & Discover5 min
- 4Reflect5 min
🎯 Learning objectives
After completing this lesson, the child should be able to:
- Discover that shape matters more than material for floating
- Build and test a foil boat, then improve it
- Explain why heavy ships float in your own words
❓ Question
How can a heavy metal ship float when a small coin sinks?
👀 Observation
Watch a coin drop in water: plop, straight down. Now picture a ship: huge, heavy, made of metal — floating. The only difference you can see? The ship has a special shape, and it is full of air inside.
🔮 Prediction
We will test two foil shapes: a tight ball and a boat. Predict: which floats? And how many marbles can your boat carry before it sinks — 3? 10? 25? Write your number down!
🧪 Exploration
Take two squares of foil. Squash one into a tight ball. Fold the other into a boat with raised sides. Float the ball (glub!), then float the boat and add marbles one at a time. Count carefully!
🔍 Discovery
The ball sinks; the boat floats. Your boat held far more marbles than you predicted, didn\'t it? The same foil, two different fates — the only thing that changed was the shape.
💡 Explanation
Floating is about pushing water out of the way. A wide boat shape pushes away lots of water and traps air — so the water pushes back and holds it up. A tight ball pushes away only a little water. Big shape, big push — that is the whole secret of ships!
✏️ Practice
Design challenge: build a second boat that can carry more marbles than the first. What will you change — taller sides? A wider bottom? Test your idea, then try the Prediction Quiz.
🪞 Reflection
What would happen to your boat on wavy water? Why do real ships have a pointy front? Wonder, guess, and maybe test in the bathtub with your grown-up\'s permission!
🧪 Materials for this experiment
Kitchen foil · a bowl of water · marbles or small stones · a notebook for your predictions and results