5. Energy Changes

Question 1

What is an endothermic reaction?

Answer 1

Endothermic items make the surroundings colder and object warmer as heat is taken from the surroundings and transferred to the object. E.g. an ice pack

Question 2

What is an exothermic reaction?

Answer 2

A reaction which makes the surroundings warmer and object colder as heat is transferred from the object to the surroundings. E.g. a fire

Question 3

What does a reaction profile for an endothermic reaction look like?

Answer 3

The reactants’ energy level is lower than the products’ and the energy increases because energy is taken in from the surroundings to the system.

Question 4

What does the reaction profile for an exothermic reaction look like?

Answer 4

The reactants’ energy level is higher than the products’ and the energy level decreases because energy is given out to the surroundings from the system.

Question 5

What is activation energy?

Answer 5

The minimum amount of energy needed to start a reaction

Question 6

What is bond breaking?

Answer 6

An endothermic reaction that takes in energy. More heat energy is taken in to break the bonds in the reactants than was given out to make the bonds in the products.

Question 7

What is bond making?

Answer 7

An exothermic reaction that gives out energy. More heat energy is released when making the bonds in the products than was taken in to break the bonds in the reactants.

Question 8

How to calculate bond energy and what do the answers mean?

Answer 8

Reactants - products
If the answer is negative, the reaction was exothermic (it takes more energy to make the bonds than break them)
If the answer is positive, the reaction is endothermic (it takes more energy to break the bonds then make them)