FACTORS THAT AFFECT RATES OF REACTION Chapter 7.3

COLLISION MODEL States that the rate of reaction is affected by the number of collisions of reactant molecules. Molecules in a gas or a liquid are constantly colliding with each other.

4 FACTORS There are four factors that affect the rate of reaction. TEMPERATURE CONCENTRATION SURFACE AREA CATALYSTS

TEMPERATURE Higher temperatures increase the rate of a chemical reaction because particles move faster at high temperatures and this creates more violent collisions more often.

CONCENTRATION Higher concentration increase the rate of a chemical reaction because there are more particles to collide with.

SURFACE AREA A larger surface area increases the rate of a chemical reaction because there are more exposed particles in the compound.

CATALYSTS A substance that increases a chemical reaction but does not get consumed by the reaction. Therefore it is not considered a reactant or product. Works by reducing the energy needed to break bonds, provides easier paths for reactions.

QUESTION Explain how you would use your knowledge of factors that affect the rate of reaction to cook a steak as quickly as possible. Temperature – increase to high Surface Area – Cut steak into pieces (increase area) Concentration – none Cataylsts - none

QUESTION What effect on the rate of reaction of a metal with 20 ml of dilute acid at room temperature would you expect if: A) the acid was cooled to 100C? B) 2 ml of concentrated acid was added? C) the metal was ground into powder before addition to the acid?

ANSWER A) The reaction rate would decrease (slow down) B) the reaction rate would increase ( speed up) C) the reaction rate would increase ( speed up )