Here are some free science games that I like. Since the computer does not read the words to you I might do the games as a whole group. For students who can read these would be great independent work.
Plants and animals
Parts of a plant
Motion and resistance
Earth Moon and Sun
Friction- this would be fun to play and then try making a model of their car track to experiment with
Here is a list of the topics covered on this site. It includes games, quizzes, video and experiments to try.