Chemical Reactions and Reaction Rates

Reaction Rates Reaction rates tell you how fast a reaction is occurring. Dynamite explodes very quickly A leaf changing colors takes a long time.

Reaction Rates The reaction rate also tells you how fast all the reactants are being consumed.

Chemical Reactions Chemical reactions involve collisions between particles of the reactants. If the collisions occur more frequently the reaction occurs more quickly If they occur less frequently, the reaction occurs more slowly.

Reaction Rates Factors that effect reaction rates include: Temperature Surface area Concentration Stirring Catalysts pH

Catalyst Catalyst- Is a substance that affects the reaction rate without being used up in the reaction. (not one of the products or reactants) Catalysts works by lowering the activation energy of a reaction

Activation Energy Activation energy- Amount of energy needed to start a reaction The spark of the igniter on your grill provides the activation energy to burn the propane.

Catalysts A catalyst often provides a surface on which a reaction can take place, where the reactants can come together.

Enzymes Enzymes- Proteins that act as biological catalysts. Biology- Study of life Enzymes speed the reactions that take place in cells and lower activation energy.

Enzymes as catalysts Enzymes are very specific catalysts One enzyme will usually catalyze only one reaction. An enzymes name is usually derived from the reaction it catalyzes, and they usually end in -ase.

Enzyme-Substrate Complex The reactants in an enzyme catalyzed reaction are called substrates. The enzyme provides a site where the substrates can bind to which allows the reaction to proceed at a faster rate.

Active Site The region of the enzyme where substrates bind is called the active site.

Enzymes as Catalysts Because enzymes are catalysts they can be affected by any changes in a chemical reaction. Temperature and pH are the two most common and important variables that affect enzyme catalyzed reactions.

Enzyme Function Most enzymes produced by human cells work best at 37°C, the average human body temperature.

Enzymes