Many good seventh grade science experiments attempt to answer a fundamental question such as "Do all liquids evaporate at the same rate?", "Does tea stain teeth?" or "Does aspirin help plants grow?" Most experiments at this grade level involve physical, chemical or biological sciences at a practical level.
In an experiment to discover if all liquids evaporate at the same rate, the student places beakers with the same amount of different liquids, such as water, orange juice, alcohol and nail polish remover, in a dry location. The student checks the level of liquid in each beaker every day for a week and records the results.
To test whether tea stains teeth, a student uses a hollowed out eggshell as a substitute for human teeth. The student fills three containers with tea, cola and coffee, and places an eggshell in each. The student checks each eggshell for discoloration every day for a week and records the results.
To see if aspirin helps plants grow, students plant seeds in two separate pots of soil, and place them side-by-side in a sunny location. The student fills one container with plain water, and a second with water in which she has dissolved two aspirin tablets. The student waters the seeds in one pot with water and the other with the aspirin solution every day for a week. The student should note which plant germinated first, the rate of growth of each plant and its overall health.