Advanced Chemical Principles and Molecular Dynamics · 6th Year

Active learning ideas

Collision Theory and Activation Energy

Kick off this topic by asking students why a match needs to be struck to light it. This simple action is a perfect analogy for activation energy, the initial 'push' needed to get a reaction going.

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

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

Activity 01

• Simulation Game
• 15 min · Small Groups

The Marble Hill Analogy

Students roll marbles with varying force up a small ramp or 'hill' into a collection tray. Only marbles with enough energy to get over the hill (activation energy) will 'react' and fall into the tray, demonstrating the energy requirement for a successful collision.

Explain the concept of activation energy using an analogy.

Facilitation Tip

Use a two-sided ramp to also model the difference between exothermic and endothermic reactions.

What to look for

Exit ticket: Ask students to draw and label a reaction profile diagram for an endothermic reaction, clearly indicating the reactants, products, activation energy, and ΔH.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 02

• Simulation Game
• 20 min · Pairs

Glow Stick Kinetics

Students place glow sticks in beakers of water at different temperatures (e.g., ice water, room temperature, warm water). They observe and record the relative brightness, linking higher temperature to more energetic collisions and a faster reaction rate.

Justify why not all collisions between reactant particles lead to a reaction.

Facilitation Tip

Ensure the warm water is not boiling, as this can damage the glow stick casing.

What to look for

Past paper question: Provide a Leaving Cert style question that requires a detailed explanation of how increasing temperature affects reaction rate, with explicit reference to activation energy and effective collisions.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 03

• Simulation Game
• 10 min · Individual

Orientation Puzzles

Provide students with molecular models or even simple jigsaw puzzle pieces that only fit together in one specific orientation. They attempt to 'collide' the pieces randomly, noting how few attempts are successful, thus illustrating the importance of correct collision geometry.

Analyse the key principles of the collision theory.

Facilitation Tip

Relate this directly to the 'lock and key' model they may have encountered in biology for enzymes.

What to look for

Traffic light cards: Students use red, amber, or green cards to indicate their confidence in explaining the two conditions for an effective collision.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

A few notes on teaching this unit

Begin with a simple analogy, like kicking a football over a hill, to introduce activation energy. Then, use a physical or virtual simulation to model the concepts of collision frequency, energy, and orientation. Finally, solidify their understanding by connecting the theory directly to the features of a reaction profile diagram, which is a common exam component.

Following this lesson, students will be able to articulate the two crucial conditions for a reaction to occur and use this theory to explain why reaction rates change.

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Watch Out for These Misconceptions

• Any collision between reactant particles will result in a chemical reaction.

  A reaction only occurs if the colliding particles have energy equal to or greater than the activation energy AND they collide with the correct geometric orientation.

• Activation energy is a type of energy that is 'used up' or consumed during the reaction.

  Activation energy is the minimum energy barrier that must be overcome for a reaction to start. It is not a reactant and is not consumed; it determines the rate, not the overall energy change of the reaction.

• A fast reaction must release a lot of energy (be highly exothermic).

  The speed of a reaction (kinetics) is determined by the activation energy, while the energy released or absorbed (thermodynamics) is determined by the overall enthalpy change (ΔH). These two factors are independent of each other.

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Methods used in this brief

• Simulation Game