In this one-session hands-on live course, we will build and race air-powered Lego cars.  Materials needed include Legos (wheels, base for cars, blocks), straws, balloons, scissors, and packing tape.  Each student will build two cars, with only one thing different between them.  For example, one child may have two identical cars but the exhaust pipe (the straw) on one will be longer than the other.  By racing both cars, that child can answer the question, How does the length of the exhaust pipe affect the distance a car travels?  Other possible variables to change include the size of the wheels, the surface driven on (rug versus wooden floor), how much the balloon is inflated, the number of balloons, etc.