Advanced Chemical Principles and Molecular Dynamics · 6th Year

Active learning ideas

Reaction Profile Diagrams

Let's map out the energy journey of a chemical reaction. These diagrams show us the 'hill' molecules must climb to transform and whether they release or absorb energy overall.

• NCCA Curriculum Specifications
• Leaving Certificate Chemistry Syllabus: Physical Chemistry - Rates of Reaction

• 10–20 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Concept Mapping
• 20 min · Pairs

Whiteboard Reaction Stories

In pairs, students are given cards with data for different reactions (e.g., ΔH = -92 kJ/mol, Ea = 150 kJ/mol). They must draw the corresponding reaction profile diagram on a mini whiteboard, labelling all key features.

Analyse a reaction profile to determine if a reaction is exothermic or endothermic.

Facilitation Tip

Encourage students to use different coloured markers to clearly distinguish the activation energy from the enthalpy change.

What to look for

Use a 'show-me' activity with mini whiteboards. Present an unlabelled diagram and ask students to circle the activation energy or calculate the enthalpy change.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 02

• Concept Mapping
• 15 min · Individual

Catalyst Sketch Challenge

Provide students with a pre-drawn reaction profile for an uncatalysed reaction. Their task is to accurately draw and label the reaction profile for the same reaction in the presence of a catalyst on the same set of axes.

Compare the reaction profiles for a reaction with and without a catalyst.

Facilitation Tip

Remind students that a catalyst does not change the energy of the reactants or products, only the path between them.

What to look for

In a topic test, provide students with energy values for reactants, products, and the activated complex, and require them to draw and fully label the corresponding reaction profile diagram.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 03

• Concept Mapping
• 10 min · Whole Class

Human Energy Profile

Use a chair or a stack of books as an 'energy barrier'. Students physically walk over the barrier to model a reaction, representing the activation energy needed to get from 'reactants' on one side to 'products' on the other.

Explain the meaning of the activated complex in a reaction profile.

Facilitation Tip

Ask students to pinpoint the exact moment they represent the 'activated complex' at the peak of the energy barrier.

What to look for

Provide a 'traffic light' worksheet where students colour-code their confidence level (red, amber, green) against each of the learning objectives for the topic.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

A few notes on teaching this unit

Begin with a simple analogy like pushing a ball over a hill to explain activation energy and net energy change. Consistently model the correct labelling of axes and key features. When introducing catalysts, draw the new pathway directly onto the original diagram to highlight that only the activation energy changes.

Students will become proficient at drawing these diagrams from data and interpreting them to explain reaction energetics and the role of catalysts.

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Watch Out for These Misconceptions

• A catalyst adds energy to the reaction to make it go faster.

  A catalyst does not provide energy. It provides an alternative reaction pathway with a lower activation energy, meaning more particles have sufficient energy to react upon collision.

• Exothermic reactions are always fast, and endothermic reactions are always slow.

  The speed of a reaction is determined by its activation energy, not its enthalpy change. A highly exothermic reaction, like the rusting of iron, can be very slow if it has a high activation energy.

• The activated complex is a stable intermediate product.

  The activated complex is a highly unstable, temporary arrangement of atoms that exists at the peak of the energy barrier. It immediately breaks down to form either products or reactants.

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Methods used in this brief

• Concept Mapping