Editing Chemical kinetics (section)

===Surface area of solid state ===
In a solid, only those particles that are at the surface can be involved in a reaction. Crushing a solid into smaller parts means that more particles are present at the surface, and the frequency of collisions between these and reactant particles increases, and so reaction occurs more rapidly. For example, [[Sherbet (powder)]] is a mixture of very fine powder of [[malic acid]] (a weak organic acid) and [[sodium hydrogen carbonate]]. On contact with the [[saliva]] in the mouth, these chemicals quickly dissolve and react, releasing [[carbon dioxide]] and providing for the fizzy sensation. Also, [[fireworks]] manufacturers modify the surface area of solid reactants to control the rate at which the fuels in fireworks are oxidised, using this to create diverse effects. For example, finely divided [[aluminium]] confined in a shell explodes violently. If larger pieces of aluminium are used, the reaction is slower and sparks are seen as pieces of burning metal are ejected.