Energy in reactions In a chemical reaction heat can be released or absorbed.

Exothermic The reaction releases heat energy Reactant --  Products + energy Ex. handwarmers

Endothermic The reaction absorbs heat energy Reactant + energy --  Products Ex. Cold packs

Factors that change reaction rates Temperature of environment Concentration (amount of substance in a certain volume) Surface area- exposed area of reactant particles

Inhibitors Substance that slows down reaction rate Ex. BHT- food preservative –Some medication

Catalysts Substance that speeds up reaction rate by lowering the activation energy Does not get used up in the reaction Ex. Catalytic converter

Enzymes Protein molecules that act as catalysts in your body’s cells Ex. Lactase, pepsin, catalase

Catalase and hydrogen peroxide 2H 2 O 2 → 2H 2 O + O 2 This is normally a very slow reaction and build up of hydrogen peroxide is toxic to cells. Bacteria cells do not produce catalase