The comparison of the masses of equal volumes of material is also defined as

chemical energy into thermal energy

Explanation:

The chemical energy is found within the chemical bonds of the acetylene fuel molecules. The amount of energy generated when the fuel is burned in the presence of oxygen is strong (using an exothermic process) and generates a flame.

The flames are warm enough to fuse metal. Melting arises as molecules are excited by the thermal energy, and they start to move rapidly and resolve the metal lattice bonding.

Hence, the first option is correct