FOSSweb is the online component of the exceptional Science curriculum developed by the University of California. It has a series of great science experiments that English Language Learners can explore online. The activities are based on grade levels — from kindergarten to middle school. You need a password to access the middle school exercises, but you can obtain that in less than a minute.
You access all of the activities from the link earlier in the post. However, I have them listed on my Science Page (just above “Planets and Space”) as Fossweb 1, Fossweb 2, and Fossweb 3. If students go to the activities via these links, then they won’t necessarily see the grade levels associated with each activity. If possible, I try to avoid having my high school English Language Learner students see that they are doing activties designed for elementary school students.