Double Trouble

When the sides of a square are doubled, what happens to the area? What happens to the diagonal of the square? When the sides of a cube are doubled, what happens to the volume? Which, if any, of these cases, involves a proportional relationship? Explain.

Extension 1
How would your answers change if you were looking at a different figure, like a circle?

Extension 2
If density = mass/volume, how could you use proportions to determine the mass of an extinct dinosaur given the density of a reptile is approximately 0.9 kg/liter.