c5 - energy changes

Question 1

what is an exothermic reaction?

Answer 1

an exothermic reaction is when heat EXITS the reaction into the surroundings

TEMPERATURE OF SURROUNDINGS INCREASE

Question 2

examples of exothermic reactions

Answer 2

combustion
hand warmers
self heating cans (eg- for food or drink)

Question 3

what is an endothermic reaction?

Answer 3

an endothermic reaction is when heat enters the reaction from the surroundings

TEMPERATURE OF SURROUNDINGS DECREASES

Question 4

examples of endothermic reactions

Answer 4

thermal decomposition
ice packs

Question 5

what are exothermic energy changes shown as?

Answer 5

Exothermic energy changes are shown as negative - ΔH

Why?

BECAUSE ENERGY IS LOST FROM THE CHEMICALS AND GONE
INTO THE SURROUNDINGS

Question 6

what are endothermic energy changes shown as?

Answer 6

Endothermic energy changes are shown as positive + ΔH

Why?

BECAUSE ENERGY IS GAINED FROM THE SURROUNDINGS

Question 7

bond energy for exothermic reactions

Answer 7

bond making = energy OUT

Question 8

bond energy for endothermic reactions

Answer 8

bond breaking = energy IN

Question 9

reaction profile for exothermic reactions

Answer 9

on google classroom slides

Question 10

reaction profile for endothermic reactions

Answer 10

on google classroom slides

Question 11

what is meant by activation energy?

Answer 11

the minimum amount of energy needed to start a reaction