CATALYSTSCatalysts are substances used to increase or decrease the rate of a chemical reaction. A catalyst is a substance that alters the rate of a chemical reaction but remains chemically unchanged at the end of the reaction. The word catalysts originally comes from the word catalysis which means the change in the rate of a chemical reaction. Catalysts, unlike other substances, can participate in many chemical transformations but are never consumed by the reaction itself. This means that when a catalyst is added to two substances to increase the rate of reaction between them, the catalyst is not consumed and can be used again.([3]"Chem4Kids.com: Reactions: Catalysts and Inhibitors.") For example, the decomposition of hydrogen peroxide; in this chemical reaction, manganese oxide can be used as a catalyst. By using manganese oxide, the reaction will occur faster but, despite this, the manganese oxide itself will not be consumed. Catalysts that speed up the reaction rate are known as positive catalysts while others that slow down the reaction rate are known as inhibitors or negative catalysts. Scientifically speaking, catalytic reactions are the fastest chemical reactions. The speed of the reaction depends on the frequency of physical contact of the two reactants. The more they collide, the more activation energy is produced and therefore the faster the reaction. However, although catalysts are not consumed by the chemical reaction itself, they can be inhibited, destroyed or deactivated. But catalysts nevertheless allow a suitable local environment to favor the reaction of one or more chemical reactions. ([6]"The effect of catalysts on reaction rates." Chemguide) Technically, the importance of catalysts pl...... at the heart of the document......CHEM4KIDS.COM by ader. Network. 08 October 2011. .[4]Creative Chemistry - Fun activities, worksheets, games and review quizzes. Network. 08 October 2011. .[5]"Dubai traffic pollution is among the worst in the world - ArabianBusiness.com." Middle East business news, Gulf financial and industrial events and information - ArabianBusiness.com. Network. 08 October 2011. .[6]"The effect of catalysts on the reaction rate." Chemguide: helping you understand chemistry - Main Menu. Network. 08 October 2011. .[7]"Power gains from a sports catalyst." Tuning and modified cars: practical guides. Network. 08 October. 2011. .