Technologies K–10 · Kindergarten

Foil boats: designing a boat that carries the most coins

Design and Production (NSW Science and Technology K–6, 2017); Design and Technologies: Processes and production skills, Designing and making (ACARA v9)

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

The same square of foil carries far more coins when it is shaped into a boat with walls, because the boat can push aside more water before it floods.

What you need

3 squares of kitchen aluminium foil, 15 cm × 15 cm, cut by the teacher, one with fold lines ruled 2.5 cm in from each edge, per pair
1 tub of tap water at least 20 cm across and 8 cm deep
25 twenty-cent coins per pair (11.3 g each, Royal Australian Mint)
1 ruler and 1 kitchen scale reading to 1 g, for the teacher (fold lines, and one foil square's mass for the simulation, found by weighing 10 squares together and dividing by 10, because a single square is lighter than the scale's smallest division)
Towels

How to do it

Squash the first foil square into a ball. Put it on the water and add coins one at a time until it sinks. Count the coins it held.
Lay the second square flat on the water and add coins the same way.
Fold the third square into a boat: fold up the walls along the ruled lines around the square floor and pinch the corners.
Guess how many coins the boat will carry and draw the guess.
Add coins one at a time, spreading them over the floor, until water comes in. Count the coins.
Record the three counts on a picture chart. Change one thing, such as taller walls or a wider floor, and test again.

What you should see

The ball and the flat sheet hold only a few coins before water floods over them; the boat holds many more. A boat of this size can never carry more than 22 twenty-cent coins, and the simulation gives 21 once the foil square's mass reaches 1.0 g, which is why the squares are weighed 10 at a time: even filled to the brim the boat pushes aside only enough water to hold up that many. Real boats flood sooner because the walls bend and coins bunch to one side, so the learner knows the test worked when the boat carries clearly more coins than the flat sheet.

What changes

What you change: the shape of the foil (ball, flat sheet, boat with walls)
What you measure: the number of coins carried before sinking
What you keep the same: the same 15 cm × 15 cm foil square
the same coins
coins added one at a time
the same tub of water

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Metal always sinks (a metal boat floats when its shape pushes aside enough water).
More foil floats better (the shape sets how much water is pushed aside, not the amount of foil).
Where the coins go does not matter (coins bunched in one corner tip the boat and it floods sooner).

Safety card

Low riskLearners carry it out

Hazards

Spilled water makes the floor slippery
Coins are a choking hazard

Controls

Towels under the tubs and spills wiped at once
Coins counted out and back in and kept on the table

Note

No chemicals or heat. Record the activity on Primary School RiskAssess (riskassess.com.au).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K–6 Syllabus (2017), NESA. The syllabus taught in 2026; the 2024 syllabus replaces it from 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.STe-2DP-T STe-4MW-ST
Science and Technology K–6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.STE-DDT-01
Australian Curriculum v9AC9TDEFP01

Sources

The pages the author read to write this activity.

All Concept Studio activities