# Starting to build the Platonic Solids at the Curious Minds Club (St Thomas of Canterbury Primary School, 24 January 2020)

This week at the Curious Minds Club we focused on three dimensional space by starting to build the Platonic Solids.

I gave the children some Polydron equilateral triangles and showed them the net of a tetrahedron. They were able to build one quite quickly, then form it into a three dimensional object. Next up was the cube. Before handing them the pieces I asked the children if they could work out the cube’s alternative name, based on it having six faces. With a little prompting to think about which two dimensional object has six sides, one girl correctly suggested ‘hexahedron’. The children then constructed their Polydron cubes. I did not show them all 11 nets of a cube (an activity for a later date?) but let them figure it out for themselves. The next was the octahedron. I gave each child eight equilateral triangles and told them that four triangles meet at each vertex. They found this a little harder and I showed them one I had made earlier as a guide.

I decided to leave the final two Platonic solids (the dodecahedron and icosahedron) to next week as I thought it would be too much to attempt all five in one session. I got out some magnetic rods and balls (similar to Geomag but a generic version) and asked the children to make the tetrahedron, cube and octahedron in this material. The Polydron pieces are good at bringing out each face of the solid, but the generic Geomag are better at bringing out the vertex and edge.

Some of the children built quite large cubes with three rods forming an edge. They soon discovered that this made a wobbly and unstable cube, due to the degrees of freedom in a square. I encouraged them to use one rod for an edge, and they had more success this way.

Below are some of the children’s creations:

I had prepared some material on the symmetry of the Platonic solids. I showed one girl how to look at each object in three ways: face on, edge on and vertex on. I gave her two dimensional pictures of each object and a piece of mirror card, and asked her to find the lines of reflective symmetry for each object. She did really well at this activity and seemed to really enjoy looking at the objects in different ways.

We finished with a quick game of Dotty Dinosaurs. This week we played the colour matching version as a memory game.