1. The problem statement, all variables and given/known data Here are a couple of conceptual questions from my cumulative review. 1. Is energy released or absorbed when a gas changes to a liquid? 2. If a yo-yo is being whirled around by its string in a vertical circle, does the string apply an outward force or an inward force? 2. Relevant equations N/A 3. The attempt at a solution I think that energy is released when a gas changes to a liquid, and I believe that the string is applying an inward force.