It is so hard for many students to understand why we balance equations at first. I created this 3D coloring worksheet to illustrate the difference in coefficients and subscripts in chemical equations.
This worksheet starts off easy and gets harder, requiring the student to think more and more as they work through it. On the first page I have drawn everything for the student and they just have to count the molecules and balance the equation. Starting on the second page they have to draw in more and more of the molecules, forcing them to make the connection between the illustrations and the equation.
If you are teaching an honors or AP class and don't have time to cover this, consider using just the answer key as a handout to illustrated the principle of balancing equations.