Universe Cycle - Earth (K)
Pre Lab 

  • Discovering the shape of the Earth.
  • Exploring the composition of the Earth.
  • rocks
  • round
  • spherical
  • crayons
  • geometric shapes (optional)
  • playdough
  • worksheet

Students make models of the Earth using playdough.


Geometric shapes help students to describe natural objects. However, real things rarely have shapes as perfect as those created by a ruler or a computer. This sometimes confuses children. They imagine the perfect geometric shape, but the real object is imperfect. Learning different shapes by using models thus enriches a child’s understanding of shapes, but does not fully define the appearance of natural objects. Students must learn that shapes are only guides to the characteristics of real things.

Children naturally see the world in three dimensions. At an early age, however, they should begin to distinguish three dimensional shapes from their two dimensional equivalents. They must learn that when three dimensional shapes are drawn on a flat surface, they usually appear or "become" two dimensional. Since this adjustment is natural for adults, they usually guide students’ understanding of this distinction poorly. It is important to give students examples of equivalent three dimensional and two dimensional objects. For instance, if you show the students a globe, also show them a circle drawn on the board or on paper.

In this exercise, the students are introduced to different shapes - a cube, a hexagon, and a circle. They will try and determine which of these is most similar to the Earth’s shape. Most children know that the Earth is spherical, but when asked, they will say the two dimensional term, circle. Make sure the students begin to understand the distinction between a sphere and a circle.

  1. If you have a set of geometric models, you may wish to use them to demonstrate different shapes to the class. Make sure to show the students the two dimensional equivalents of the shapes as well.
  2. Have the students complete the upper part of the worksheet.
  3. Ask students how we know that the Earth is spherical. Most children have seen pictures of Earth from space, or have seen a globe, so they know that the shape is spherical. You can tell the students that hundreds of years ago people thought the Earth was flat and that ships could sail off the face of the Earth. People slowly began to realize that ships coming from long distances appears from the top of the mast before the entire ship could be seen.
  4. The lower part of the worksheet has students think about what is inside the Earth. Evidence about this is more difficult to observe than the shape of the Earth. Most students eventually arrive at the correct answer, "rocks" by a process of elimination. This is basically correct; the Earth is basically a ball of rock that is rotating and revolving in space. The interior of the Earth is very hot, but there is no fire per se within it.
  5. As an added exercise, you may want to give students playdough , and have them fashion a spherical "Earth." Here are a pair of playdough recipes:
    PLAYDOUGH RECIPE #1 (the dough formed is not as durable as recipe #2)
         1 cup flour
         1\2 cup salt
         2 teaspoon cream of tartar
         1 cup water

    RECIPE #2. CLASSROOM QUANTITIES (alum helps preserve the playdough)
         5 cups of flour
         1 cup of salt
         2 tablespoons of alum
         2 tablespoons oil
         3 cups of very hot water
    For both recipes, first mix together all the ingredients. Cook them over medium heat while stirring, for 3 to 4 minutes, until a dough ball forms and separates from the sides of the pan. You may add food coloring or glitter for special effects. Adding food coloring works best when it is added with the water at the start of the recipe.

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