Energy change & Rates of Reactions Definitions

Question 1

heat of reaction

Answer 1

the net change of chemical potential energy of the system

Question 2

exothermic reactions

Answer 2

reactions which transform chemical potential energy into thermal energy

Question 3

endothermic reactions

Answer 3

reactions which transform thermal energy into chemical potential energy

Question 4

activation energy

Answer 4

the minimum energy required the start a chemical reaction OR the energy required to form the activated complex

Question 5

activated complex

Answer 5

a high energy, unstable, temporary transition state between reactants and products

Question 6

reaction rate

Answer 6

change in concentration per unit time of either a reactant or product

Question 7

catalyst

Answer 7

a substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Question 8

collision theory

Answer 8

model that explains that a reaction will only proceed when reactant particles collide effectively. An effective collision is one in which the colliding particles have:

• the correct orientation
• sufficient energy