Energy Changes

Question 1

What is activation energy?

Answer 1

Activation energy is the least amount of energy that colliding reactant particles must possess to react with each other.

Question 2

What is bond energy?

Answer 2

Bond Energy is the amount of energy absorbed to break one mole of a chemical bond/amount of energy released when one mole of a chemical bond is formed.

Question 3

What is an exothermic reaction

Answer 3

Exothermic reaction is a process or a chemical reaction which transfers heat to the surroundings (may be detected by an Increase in Temperature)

Question 4

Examples of exothermic reaction

Answer 4

• Combustion of Fuels
• Neutralisation
• Dissolving of Acids and Alkalis in water
• Respiration
• Rusting
• Oxidation
• Freezing Processes (e.g condensation )

Question 5

What occurs in exothermic reactions?

Answer 5

• In exothermic reactions, there occurs bond making. → Energy is released when bonds are formed
• Total energy absorbed during bond breaking < Total energy released during bond making
• ∆H is Negative

Question 6

What is an endothermic reaction?

Answer 6

Endothermic Reaction is a process or chemical which takes in heat from the surroundings. (may be detected by an decrease in temperature)

Question 7

Examples of endothermic reaction

Answer 7

• Thermal Decomposition of Metal Carbonates to Metal Oxides and Carbon Dioxide gas
• Photosynthesis
• Dissolving of some ionic compounds in water e.g ammonium chloride, ammonium nitrate, sodium chloride
• Boiling Processes ( e.g Sublimation, Vaporisation)

Question 8

What occurs in endothermic reaction?

Answer 8

• In endothermic reactions, there occurs bond breaking. → Energy is absorbed when bonds are broken.
• Total energy absorbed during bond breaking > Total energy released during bond making
• ∆H is Positive