Use toothpicks as edges and mini marshmallows (or small balls of dough) as joints to build simple geometric shapes — triangles, squares, pyramids — then combine them into a small freestanding tower. Compare which shapes hold up under gentle pressure and which collapse.
What you need
- toothpicks
- mini marshmallows or small dough balls
How to do it
- 1Build a simple triangle from three toothpicks and three marshmallow joints, then a square from four.
- 2"Push gently on both — which one holds its shape?" Compare how each responds to light pressure.
- 3Combine several triangles into a small pyramid or tower shape, using the sturdier shape as the base.
- 4Keep building upward until the tower reaches its natural limit and test how much it can hold.
Variations
- If marshmallows aren't available: small balls of play dough work identically as joints.
- How it ends: a final height measurement or a gentle 'earthquake test' (a light shake) gives the build a clear conclusion.
💡 Parent tip
Let a square tower collapse before suggesting triangles — discovering the fix themselves sticks far better than being told in advance.
What your child develops
- Geometry in practice — directly comparing why triangles are more stable than squares
- Structural engineering basics — building up from a stable base shape
- Fine motor precision — inserting toothpicks into small joints without breaking them
Safety notes
- Toothpicks are sharp — supervise closely and keep away from younger siblings who might handle them unsafely.
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