When ice is left outside on a hot day, it melts, and then evaporates. which best describes what happens to the molecules in the ice?

This doesn't seem like much of a biology question but more of a chemistry one :P

But to answer your question, as the temperature of the water molecules rises, the chemical bonds holding them together begin to fall apart, causing the structure of the ice to fall apart.

When water is evaporated, the chemical bonds holding the water molecules together becomes non-existent, and the water becomes a vapour in which molecules float independent of each other 

Due to the amount of pressure