Science fair ideas for kids include performing helmet crash tests and measuring the corrosiveness of soda. Both experiments require minimal materials and only a little adult supervision.
Kids need honeydew melons, a ladder and a variety of helmets to perform the helmet crash tests. The kids fit the melons snugly in the helmets, then climb on the ladder and drop a melon without a helmet for the control. They then drop the melons in the helmets from the same height and in the same way. Afterward, they record the damage to the melons.
To measure the corrosiveness of soda, kids place pennies face-up in a container and pour soda over them, then leave the pennies overnight. The pennies should then be shiny on the side exposed to the soda.