13. The boiling point is 80°C, and the melting point is 20°C.
14. [Well I'm not exactly sure what it's asking, but I'll say what I assume it's asking] The substance has changed state from a solid to a liquid, and the particles in the substance start to/continue to gain more energy as it is being added, allowing the particles to move around more.
I've included a picture that may help a bit.