To begin conducting this experiment you will need to place several bread slices on a clean surface. Fill a small glass with water. Have your child take the eye dropper and fill it with water. Allow your child to place drops of water on each bread slice. Decide on three different moisture levels for the bread slices and make two of each moisture level.
Once you have each slice of bread moistened, place each piece of bread in a sandwich bag and seal it. Label each bag with a description of which sample it is. Place one of each of the samples in the light and one of each of the samples in the dark. As the mold grows over time have your child track the mold growth. At the end of the project have them note the differences of growth in the mold on the bread in the light and the dark.
Easy science projects like this are great because you can come up with many different ways to create new variables in your test subjects. Kids will enjoy varying this experiment using different kinds of bread, stale bread, fresh bread, bread with food coloring. It is a great way to show them how small differences can yield significant results.