A continuation of our exploration of topology. An explanation of the rules of deformation (no new holes, no filling in holes, no gluing, no tearing), followed by getting out the modelling clay and deforming a torus (or doughnut) into a coffee mug. An extension of this by deforming a two-hole torus into a pair of pants, and a three-hole torus into a vest (after explaining why a vest has three holes).

A new activity to demonstrate that topology includes changing an object’s shape without changing its size. Cutting a hole the size of a 5p in a piece of paper, trying to pass a 2p through this hole, finding this is impossible in 2D space, switching to 3D space by lifting up the piece of paper and introducing height, and finding that the 2p will pass through the hole once the paper is twisted and manipulated.