Raul- I don't have any specific recommendations- but have you used Graphite? I just did a search at that site and got 128 resources- you can then go through them and read the reviews and ratings from other teachers.
Although it is not a game if you are looking for a tool or resource that helps students organize their thoughts and make a claim/prove a hypothesis I suggest checking out Intel's Showing Evidence The project examples are a great place to get started.
Raul, I have also not seen any free downloadable games for Scientific Inquiry. As julesfischy suggested, Graphite provides tested links for school appropriate websites. I often use the pHET simulations - they are not games, but teach scientific principles. Please share the resources you decided to use.