Take out a pen/paper or use your iPad.
The student sitting on the right side of the pair moves in a snake shape one seat when the timer runs out.
You each get 2 minutes to explain your topic to the other student.
The other student takes notes on your topic.
After 2 minutes, you swap roles.
After 4 minutes, one student moves to a different seat (in the same snake-like pattern), to talk to a different classmate about their topic, and learn about a new topic.