Download Controlling Chemical Reactions

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.