Energy Changes in Chemistry
This lesson introduces Year 10 students to the concept of energy changes in chemical reactions. Students will learn to categorise reactions as exothermic or endothermic, interpret energy level diagrams, and perform quantitative bond energy calculations.
Learning objectives
- Distinguish between exothermic and endothermic reactions based on temperature change.
- Draw and interpret reaction profile diagrams including activation energy.
- Calculate the overall energy change of a reaction using bond energies.
Lesson plan (60 minutes)
Introduction · 5 min
Do Now: Students recall the definitions of chemical and physical changes and give examples.
Instruction · 10 min
Teacher Explainer: Direct instruction on exothermic and endothermic reactions using the provided script and diagrams.
Demonstration · 10 min
Demonstration/Video: Watch a simple neutralisation (exothermic) and thermal decomposition (endothermic) and record temperature changes.
Guided Practice · 10 min
Worked Example: Step-by-step walk-through of a bond energy calculation on the board.
Independent Practice · 20 min
Differentiated Worksheet Activity: Students work through Support, Core, or Stretch tasks based on prior attainment.
Review · 5 min
Plenary: Multiple-choice quiz to check for misconceptions and consolidate learning.
Key vocabulary
- Exothermic
- A reaction that transfers energy to the surroundings (usually as heat).
- Endothermic
- A reaction that takes in energy from the surroundings.
- Activation Energy
- The minimum amount of energy needed for a chemical reaction to occur.
- Reaction Profile
- A diagram showing the relative energies of reactants and products.
- Bond Energy
- The energy required to break a specific chemical bond.
Core worksheet (first questions)
- Define an exothermic reaction in terms of energy transfer.
- Explain the difference between bond breaking and bond making in terms of energy.
- In an exothermic reaction, do the reactants or products have more energy? Why?
- What is 'activation energy'?
Quiz (sample)
1. What happens to the temperature of the surroundings during an exothermic reaction?
- A. It increases
- B. It decreases
- C. It stays the same
- D. It fluctuates randomly
2. Which of the following is an example of an endothermic reaction?
- A. Combustion
- B. Neutralisation
- C. Oxidation
- D. Thermal decomposition
3. What is activation energy?
- A. The total energy in the products
- B. The minimum energy required for a reaction to occur
- C. The energy released when bonds form
- D. The temperature of the room
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