CH 2, SECTION 3 CONTROLLING CHEMICAL REACTIONS

Every chemical reaction involves change of energy. 1.exothermic reaction= releases energy in the form of light, electrical, or heat 2.endothermic reaction= absorbs energy

Energy Diagrams An energy diagram shows what is happening with the energy during a chemical reaction. Some chemical reactions will release energy and some will absorb energy. The diagram is a visual way to represent whether energy is being released or absorbed.

Energy Diagrams Energy is released! Energy is absorbed! Exothermic Endothermic

activation energy minimum amount of energy that has to be added to start a reaction

Factors that affect rate of chemical reactions concentrationsurface areatemperaturecatalystinhibitor

amount of material in a given volume of another material 1. concentration=

2. surface area

3. temperature

4. catalysts= lowers activation energy – enzyme= biological catalyst

CATALYSTS A catalyst is like adding a bit of magic to a reaction. Reactions need a certain amount of energy to happen. If they don't have it, oh well, the reaction probably can't happen. A catalyst lowers the amount of energy needed so that a reaction can happen easier.

5. inhibitor decreases rate of reaction

INHIBITORS Works exactly the opposite of catalysts. Slow the rate of reaction. Sometimes they even stop the reaction completely. You might be asking, "Why would anyone need those?" You could use an inhibitor to make the reaction slower and more controllable. Without them, some reactions could keep going and going and going. If they did all of the molecules would be used up. That would be bad, especially in your body.

factors that affect rate of chemical reactions: 1. Concentration 2. Surface area 3. Temperature 4. Catalysts (enzymes) 5. Inhibitors