UNIT 4 - ENERGY

Question 1

WHAT ALWAYS HAPPENS IN A CHEMICAL REACTION ?

Answer 1

There is always a transfer of energy to or from the surroundings

Question 1

WHAT IS BOND ENERGY ?

Answer 1

The amount of energy needed to break on mole of a particular bond
If more energy is taken to break the bonds than given out when new bonds are formed it is endothermic
If more energy is released when new bonds are formed than is taken in to break the existing bonds it is exothermic

Question 1

WHAT IS AN EXOTHERMIC REACTION ?

Answer 1

A reaction that gives out heat energy, causing the surrounding temperature to increase
Combustion and neutralisation are exothermic

Question 1

WHAT IS AN ENDOTHERMIC REACTION ?

Answer 1

A reaction that takes in/ absorbs heat energy, causing the surrounding temperature and mixture to decrease
Electrolysis and thermal decomposition are endothermic

Question 2

WHAT IS ACTIVATION ENERGY ?

Answer 2

The minimum energy needed to start a reaction

Question 3

HOW DO YOU CALCULATE BOND ENERGY ?

Answer 3

Calculate the energy needed to break all bonds
Calculate the energy released in the formation of all the new bonds
If the energy released is bigger than the energy taken in then it is exomthermic