Question 1: Define activation energy and explain its significance in a chemical reaction.

Answer: Activation energy is the minimum amount of energy required for particles to collide successfully and react. It determines the rate of a chemical reaction.

Question 2: Describe how activation energy influences the speed of an exothermic reaction.

Answer: Lower activation energy results in a faster reaction because more particles have sufficient energy to react at a given temperature.

Question 3: In an endothermic reaction, how does activation energy affect the temperature change of the surroundings?

Answer: A higher activation energy means the reaction absorbs more energy, often leading to a greater decrease in surrounding temperature during the reaction.

Question 4: Explain the difference between activation energy and overall reaction enthalpy change.

Answer: Activation energy is the energy barrier to start a reaction, while the reaction enthalpy change is the net energy exchanged during the reaction.

Question 5: What is the effect of a catalyst on activation energy?

Answer: Decreases activation energy

Question 6: A reaction has an activation energy of 50 kJ/mol. How does increasing the temperature affect the number of particles with sufficient energy to react? (Choose the best explanation.)

Answer: It increases the number of particles with enough energy

Question 7: Fill in the blank: The activation energy is the energy barrier that reactant particles must overcome to reach the ________ state.

Answer: activated

Question 8: Describe in brief how a catalyst affects the activation energy of a reaction and its overall rate.

Answer: A catalyst provides an alternative pathway with a lower activation energy, which increases the number of successful collisions and speeds up the reaction without being consumed.

Question 9: State two practical methods used in industry to lower activation energy and increase reaction rates.

Answer: Using catalysts and increasing the temperature of the reaction mixture.

Question 10: An experiment aims to measure the effect of temperature on reaction rate. List three variables that should be controlled to ensure a fair test, and justify each.

Answer: Variables to control include: (1) Concentration of reactants to ensure consistent collision frequency, (2) Surface area of solids to maintain consistent contact, (3) Presence of catalysts to prevent their influence on activation energy, and (4) Temperature outside the variable being tested to prevent unintended effects.

Question 11: Explain how understanding activation energy can help in designing safer and more efficient chemical processes in industry.

Answer: Understanding activation energy allows industry to optimise reaction conditions for faster reactions with minimal energy input, reducing costs and increasing safety by avoiding unintended rapid reactions. Catalysts can be used to lower activation energy, making processes more efficient and controllable.