The transfer of energy means, in convention process, transport of matter. In this case, hot water has lower density than cool water. The water with less density ascends and leaves gaps that are occupied with cooler water "packages".
A. Molecular solids tend to have lower melting points than Ionic so it would be Ionic if it weren't for Molecular.
I believe it goes as the following::
1) Waves transfer energy without moving particles
2) The two types of waves are longitudinal and transverse waves OR The two types of waves are mechanical and electromagnetic waves. Both are applicable and should be correct!
