- Slides: 11
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.