A RAFT is a short writing assignment where students take on a ROLE, address a certain AUDIENCE, in a particular FORMAT, about a given TOPIC.
For my science class, since my focus is on the SCIENCE, rather than the writing, I keep the format simple...a letter.
In this RAFT, students play the role of a proton, and choose to either write a love letter to an electron, or a letter to another proton, explaining why they can't be friends.
Included is an example of a class brainstorming session that should give you an idea of what that might look like, as well as an example RAFT, about a different science topic, so you can see how a RAFT comes together.
I typically score mine in this fashion:
Accurate and complete science content = 75%
Correct grammar/spelling = 20%
Proper format = 5%