Students still want to know how various household chemicals affect plant growth, or whether video games make them and their friends smarter. These and about 200 other student experiments will be on display Friday, April 3, when the Alabama Science & Engineering Fair returns for its 20th anniversary at The University of Alabama in Huntsville (UAH). Students also are testing the effects of temperature change on magnets, or developing a low-cost laser scatterometer that might be used as an inexpensive household air-quality monitor. Spenser Willard, an eighth grader at Grace Lutheran School in Huntsville, tested a sensor that measures movement to see if it might be used to detect when someone falls. (It can.)