Take two plants of the same species and age and place them on a naturally lit windowsill before writing "control" on one pot and "PJ" on the other. Take petroleum jelly and coat the leaves on the PJ plant so every leaf is completely covered by the jelly. Leave your plants for at least four weeks, watering both plants once every other day with a controlled level of water. Get students to write down each plant's status once a week, including the number of new leaves growing, the height and width of the plants and their apparent overall health on a scale of one to 10. Students will observe there is no new leaf growth in the petroleum jelly plant, as the leaves covered in jelly cannot photosynthesize. This plant will also start to wither and die after a while.
Your fifth-graders must carry out this simple experiment in pairs. Provide each pair with a different species of adult plant in a pot, a large sheet of paper, three colored crayons, a yardstick and a flashlight. Designate one of the young scientists as the artist while the other holds the flashlight and the yardstick. Have one of the students switch on the flashlight and hold it directly above the plant shining downwards onto it from one, two and three feet. Get the artist to draw the outline of the shadow when the flashlight is held at each different height to see how the width of the shadow is affected by the distance of the light source. This teaches your fifth grade scientists about how a plant's width can increase its ability to photosynthesize, therefore allow it to grow faster.
Your fifth-graders' ability to measure the growth and changes in plants is essential to the success of the experiment. As such, you should help them along the way as much as possible. At a fifth-grade level, for example, students looking to examine how different plants have photosynthesized can simply measure plant height and width using a ruler or tape measure. Furthermore, your young scientists can also count the number of leaves present on the plant, as this indicates the plant's physiological age. Those students wishing to take experiments to a more advanced level can also measure the surface area of plant leaves.
Alongside the recording of accurate measurements during experiments, your fifth-graders should also learn about how to handle and display experiment data. When teaching the fifth grade, emphasize the importance of making results easy to understand. Instruct your students to conduct a pair of line graphs, for example, to show how plants have been able to grow in both height and width. Your young scientists can plot a plant height line graph, for example, with height in inches on the vertical axis and time in one day increments on the horizontal.