Scale models of Earth's interior

How to build a scale model of Earth's Interior

1.  Select a round object to use for your model and measure the radius in centimeters.
2.  Create a scale for your model by making the radius of your round object equal to the radius of the Earth (6373 km).  For example, "10 cm = 6373 km".
3.  Set up a proportion for each layer of the Earth using the scale and the thickness of each layer of actual Earth.  Solve for the unknown value (? cm) given the known values (thickness of each layer of actual Earth in km).  

How to critique a scale model of Earth's Interior

1.  Measure the thickness of each layer in centimeters.
2.  Create a scale for each layer by making the number of centimeters of each layer equal to the number of kilometers of each layer in the ACTUAL interior of Earth.
3.  Calculate the scale factor each layer by dividing the number of centimeters in each layer (from the model) by the number of kilometers in each layer (of actual Earth).
4.  If the scale factor is the same for each layer, then the model is to scale!  If the scale factor is NOT the same for each layer, then the model is not to scale.