We talked about it in our chemistry class but we couldn't get to a conclusion, any help?
NO, we can't melt wood!
From primary level we have learned that solid melts to liquid at certain temperature and on increasing the temperature further it change into gaseous. But that is not the case always.
The problem with melting wood revolves around what combustion is, and what temperature the combustion of wood happens at. Combustion, also known as burning, is simply a chemical reaction that takes place where the combustible material (in this case wood) in the presence of an oxidizer (usually the air around the fire) changes its chemical composition and decomposes the material into other chemicals. The process is one that’s exothermic. As such, light and heat can be released.
Wood is mostly made up of things like cellulose, lignin, and water. As wood combusts, it’s broken down into products like charcoal, water, methanol, and carbon dioxide. Unlike water turning back into ice, if you cooled down the resulting products of burning wood, it obviously does not change back to its original composition.
All materials that combust will have a natural temperature at which the process will begin taking place. The higher the temperature, the quicker the process becomes (usually). If that temperature is lower than the temperature at which the material will melt, that material will never (naturally) melt because it just turns into other chemicals.
As for wood, it will begin a process known as pyrolysis at temperatures around 500-600 degrees Fahrenheit. Pyrolysis is also an exothermic reaction that tends to be self sustaining. At these temperatures, wood will begin giving off up to 100 chemicals, including methane and methanol (the same stuff they put as additives in gasoline), that will begin to burn. Once those chemicals begin burning, they will increase the temperature and the remaining char (the burned black bits present after the fire goes out) left behind will begin to further decompose, things like calcium, potassium and magnesium.
Theoretically, it may be possible, but hasn't been proven.
According to this article, wood cannot even be melted in a vacuum, but may be able to melt under high pressure.
The lignin, and some of the hemicelluloses, in wood can melt under certain circumstances, such as friction welding. For a dramatic video, see: https://www.facebook.com/interestingengineering/videos/1891004754302553/
Here they say, about welds created between wood pieces during friction welding: "Examination of the bondline suggests that the friction between the pieces heats and melts components of the wood (mainly lignin) and loosens fibers on the surface. These fibers intertwine in a matrix with the molten lignin and solidify to form a bond that is strong enough for structural applications."
For more details, see: "Wood Bonding by Mechanically-Induced in Situ Welding of Polymeric Structural Wood Constituents" B. Gfeller M. Properzi M. Zanetti A. Pizzi F. Pichelin M. Lehmann L. Delmotte, Journal of Applied Polymer Science 92(1):243 - 251, 2004
Abstract from above reference: "Mechanically induced wood fusion welding, without any adhesive, is shown here to yield rapidly bonding wood joints satisfying the relevant requirements for structural application. The mechanism of mechanically induced vibrational wood fusion welding is shown to be due mostly to the melting and flowing of amorphous cells–interconnecting polymer material in the structure of wood, mainly lignin, but also some hemicelluloses. This causes a partial detachment, the “ungluing,” of long wood cells and wood fibers and the formation of an entanglement network drowned in a matrix of melted material which then solidifies, thus forming a wood cell/fiber entanglement network composite with a molten lignin polymer matrix. During the welding period some of the detached wood fibers which are no longer being held by the interconnecting material are pushed out of the joint as excess fiber. Crosslinking chemical reactions of lignin and carbohydrate-derived furfural also occur. Their presence has been identified by CP-MAS 13C-NMR. These reactions, however, are relatively minor contributors during the very short welding period. Their contribution increases after welding has finished, which explains why relatively longer holding times under pressure after the end of welding contribute strongly to obtaining a good bond." © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 243–251, 2004