Question

Which change happens when a substance melts?
o Hear energy overcomes the forces of attraction between the molecules of the substance so the molecules can move more freely.
o The molecules of the substance move farther apart which pulls on the intermolecular bonds between them.
o The vibration of the molecules produces enough heat to weaken the forces of attraction between the molecules of the substance.
o Heat energy forces the molecules of the substance farther apart until the rigid structure of the solid breaks.

Answer 1

I think a is right (partly) and I also think d is right (partly) but in my opinion both a and d could be expressed more clearly. Heat increases the kinetic energy of the molecules, they can move more freely and more energetically, and at some point the attractive forces between the molecules is too small to hold them together and the rigid structure of the solid is broken.