Controlling Chemical Reactions Energy in Chemical Reactions Every

Controlling Chemical Reactions

Energy in Chemical Reactions • Every Chemical reaction involves a change of energy. Some reactions release energy others absorb energy.

Exothermic reaction • Releases heat • Car burning gasoline

Endothermic Reaction • Absorbs heat. Feels cold. • Baking Soda reacting with vinegar.

Getting Reactions Started • Activation energy-minimum amount of energy that has to be added to start a reaction.

Rates of Chemical Reactions • The rate of a reaction is affected by such factors as concentration, surface area, and temperature.

Concentration • The amount of material in a given volume of another material. • A greater concentration makes reactants more available and the rate increases.

Surface Area • Only molecules on the surface can react with each other. • Increasing the surface area increases the rate of reaction. • Ex-Crushing a solid into a powder makes it react faster with a liquid.

Temperature • Increasing temperature increases rate of reaction. • Molecules bump into each other more often and provide greater energy to get reaction started. • Example-Bacteria resperate and spoil warm food faster than bacteria on food in the refrigerator.

Catalysts • A chemical that increases the rate of a reaction by lowering the activation energy required. • Example Potassium Iodide acts as a catalyst for break down of hydrogen peroxide.

Inhibitor • Used to decrease the rate of chemical reactions. • Example- Wood Pulp was mixed with Nitroglycerin to make it more stable which became dynamite.