Verb heat up has 3 senses
  1. heat, hot up, heat up - gain heat or get hot; "The room heated up quickly"
    --1 is one way to change state, turn
    Sample sentence:
    The water heat ups
  2. heat, heat up - make hot or hotter; "heat the soup"
    --2 is one way to change, alter, modify
    Sample sentence:
    They heat up the water
  3. heat up, hot up, screw up - make more intense; "Emotions were screwed up"
    --3 is one way to intensify, compound, heighten, deepen
    Sample sentences:
    Somebody ----s something
    Something ----s something