Understanding what causes reaction to occur spontaneously, or not; fast, or slow etc is key to many industrial processes. Ideally a chemist could make any reaction (such as the splitting of water into hydrogen and oxygen), occur rapidly with very little energy input, effectively providing limitless fuel. Unfortunately this still eludes scientists who have not yet managed to come close to matching the efficiency of chlorophyll in plants. This unit is assessed externally and makes up AS 91166 (2.6). For sample exam papers and exemplar answers see here.