Physics
When steel wool is between the poles of a battery, it starts to burn. This can be used to illustrate many biblical passages where fire occurs.
Strong magnets offer many possibilities for interesting effects such as displaying magnetic fields, illustrating the invisible power of God, showing attraction/repulsion and much more.
A PET bottle is filled with hot water, emptied and quickly screwed shut. It soon contracts, although no external force is visible.
This article describes how you can build a water rocket with simple material, which flies up to 50m high!
In another article, the construction of the launch pad is then described.
This boat moves forward in the water with the energy stored in the rubber by turning the paddle wheel backwards.