It’s called the group 4 project since it involves the IB group 4 subjects (bio, physics, chem) and in layman’s terms, is just a science fair.
Here’s how ours went: our class was split in groups of 3/4 each, with each student taking either biology, physics or chemistry. Then, the organizing teacher provided us with a ‘topic’ of some sort that everyone has to incorporate into their project. Our topic was simply “Water”. Then, everyone in the group will contribute their bio/phy/chem knowledge to brainstorm a project/idea that incorporates all three sciences. You have the entire day to brainstorm, build and test your idea/project. Thereafter, after several days passed, all the groups in our class presented their projects to the Year 1’s, and they got to vote who had the best idea.
Our group did something with regards to water rockets (we won, too;) ). This is the video we showed during presentation day:
it’s really silly but doesn’t hurt to watch… and I don’t remember ESS being involved, just the three core sciences.