[LUFER]

Hello, please I need help, the text I left in bold, do not understand what he meant.

 

In all cases, however, it is the very high internal surface area of the pSi surface which permits a highly intimate mixture between the oxidising agent and the silicon. The oxidation of elemental silicon is highly exothermic, much more so than if carbon was used as the fuel instead of silicon. For example, the basic reaction of silicon and sodium perchlorate proceeds as follows:
 

 

Source: The influence of pore size and oxidising agent on the properties of porous silicon