But when carbon oxidizes--or unites with oxygen say, during burning--it becomes the gas carbon dioxide; silicon oxidizes to the solid silicon dioxide, called silica. The fact that silicon oxidizes to a solid is one basic reason as to why it cannot support life. Silicon doesn't form many compounds having handedness. Thus, it would be difficult for a silicon-based life-form to achieve all of the wonderful regulating and recognition functions that carbon-based enzymes perform for us. Despite years of work--and despite all the reagents available to the modern alchemist--many silicon analogs of carbon compounds just cannot be formed. Thermodynamic data confirm these analogs are often too unstable or too reactive.