Use precise language to describe the properties of 2D and 3D shapes, and compare shapes by reasoning about similarities and differences in properties (2)

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Description

Building on 1G–1, pupils should continue to explore and discuss common 2D and 3D shapes, now extending to include quadrilaterals and other polygons, and cuboids, prisms and cones. Pupils must now learn to use precise language to describe 2D shapes, including the terms ’sides’ and ‘vertex’/’vertices’. They should learn to identify the sides of a given 2D shape and to identify a vertex as a point where two sides meet. Pupils must learn that a polygon is a 2D shape which has only straight sides and then learn to identify a given polygon by counting the number sides (or vertices). Pupils should practise running their finger along each side as they count the sides (or practise touching each vertex as they count the vertices). Later, pupils may mark off the sides or vertices on an image as they count. It is important that they learn to count the sides/vertices accurately, counting each once and only once. Pupils must know that it is the number of sides/vertices that determines the type of polygon, rather than whether the given shape looks like their mental image of a particular polygon. For example, although pupils may informally describe the shape below as “like a square with 2 corners cut off”, they should be able to recognise and explain that, because it has 6 straight sides, it is a hexagon.

Language focus

“This shape is a hexagon because it has exactly 6 straight sides.”

“These shapes are all pentagons because they all have exactly 5 straight sides.”

When discussing 3D shapes, pupils should be able to correctly use the terms ‘edges’, ‘vertex’/‘vertices’ and ‘faces’. Pupils need to be able to accurately count the number of edges, vertices and faces for simple 3D shapes, such as a triangular-based pyramid or a cuboid, using sticky paper (if necessary) to keep track of the edges/vertices/faces as they count. Pupils should be able to identify the 2D shapes that make up the faces of 3D shapes, including identifying pyramids according to the shape of their base (‘square-based’ and ‘triangle-based’). Pupils should gain experience describing and comparing standard and non-standard exemplars of polygons. They should explore shapes (for example, shapes cut from card) rather than only looking at pictures. Examples of irregular polygons should not be restricted to those where every side-length is different and every internal angle is a different size. Examples should include polygons in which:

• some side-lengths are equal.
• some internal angles are equal.
• there are a variety of sizes of internal angles (acute, right angled, obtuse and/or reflex).
• there are pairs of parallel and perpendicular sides.

Pupils don’t need to be able to identify or name angle types or parallel/perpendicular sides in year 2, but it is important that they gain visual experience of them as preparation for identifying and naming them in key stage 2.

In a similar way, pupils should gain experience describing and comparing a wide variety of 3D shapes including cuboids (and cubes), prisms, cones, pyramids, spheres and cylinders. Pupils should explore shapes practically as well as looking at pictures. Pupils should also explore and discuss regular polyhedrons such as octahedrons and dodecahedrons, although year 2 pupils do not need to remember the names of these shapes.

As well as discussing sides and vertices (as a precursor to evaluating perimeter and angle), pupils should begin to use informal language to discuss and compare the space inside 2D shapes (as a precursor to evaluating area). Pupils should be able to reason about the shape and size of the space inside a 2D shape, relative to other 2D shapes, using language such as ‘long and thin’, ‘short and wide’, ‘larger and ‘smaller’.