Chemistry · Secondary 3

Active learning ideas

Energy Changes in Chemical Reactions

Active learning helps students visualize abstract concepts like energy transfer in chemical reactions. When students manipulate real materials or analyze diagrams, they connect abstract terms like 'exothermic' to observable temperature changes in their hands.

• MOE Syllabus Outcomes
• MOE: Chemical Energetics - S3
• MOE: Energy Changes - S3

• 15–45 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Inquiry Circle
• 45 min · Small Groups

Inquiry Circle: Hot and Cold Packs

Groups are given various salts (e.g., Calcium Chloride, Ammonium Nitrate). They dissolve them in water, measure the temperature change, and then design a prototype for either a 'hand warmer' or an 'instant ice pack' based on their data.

Differentiate between exothermic and endothermic reactions.

Facilitation Tip

During the Hot and Cold Packs activity, circulate to ensure groups measure temperature changes at consistent intervals and record data in a shared table.

What to look for

Provide students with a list of common reactions (e.g., burning wood, ice melting, respiration, cooking an egg). Ask them to categorize each as exothermic or endothermic and briefly justify their choice by stating whether heat is released or absorbed.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 02

• Gallery Walk
• 25 min · Small Groups

Gallery Walk: Energy Profile Critique

Students draw energy profile diagrams for different scenarios on mini-whiteboards. They rotate to check each other's work for correct labeling of reactants, products, activation energy, and the sign of ΔH.

Explain why the temperature of the surroundings changes during an energy-releasing or absorbing process.

Facilitation Tip

In the Energy Profile Critique Gallery Walk, assign each student a specific diagram to analyze first before they move to peer feedback.

What to look for

Pose the question: 'Imagine you are designing a chemical hand warmer. Would you want to use a reaction that is exothermic or endothermic? Explain your reasoning, referring to how the temperature of the surroundings changes.'

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

Activity 03

• Think-Pair-Share
• 15 min · Pairs

Think-Pair-Share: Surroundings vs. System

The teacher performs a demo where a beaker gets cold. Students must think about where the energy is going, discuss with a partner whether it is endo- or exothermic, and explain why the thermometer shows a decrease in temperature.

Analyze real-world examples of exothermic and endothermic reactions.

Facilitation Tip

For the Think-Pair-Share on surroundings vs. system, provide colored pencils so pairs can sketch system boundaries directly on their diagrams as they discuss.

What to look for

On an index card, have students draw a simple energy profile diagram for an exothermic reaction. They must label the reactants, products, activation energy, and indicate the sign of the enthalpy change (ΔH).

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

A few notes on teaching this unit

Teachers should introduce energy changes with concrete examples before abstract diagrams. Avoid rushing to energy profiles until students observe real temperature changes firsthand. Research shows that student-generated diagrams, like those sketched during peer discussions, improve retention of activation energy concepts more than pre-made diagrams.

Successful learning looks like students confidently distinguishing exothermic and endothermic reactions, correctly labeling energy profile diagrams, and explaining heat flow between systems and surroundings using precise vocabulary.

---

Watch Out for These Misconceptions

• During Collaborative Investigation: Hot and Cold Packs, watch for students interpreting cold packs as exothermic because they feel cold to the touch.

  Have students place the cold pack against their skin and measure the temperature of the surroundings with a thermometer, then ask them to describe the direction of heat flow in their lab report.

• During Gallery Walk: Energy Profile Critique, watch for students assuming endothermic reactions have no activation energy.

  Ask students to trace the energy path on the diagrams with their fingers to identify the 'uphill' climb before the reaction proceeds.

---

Methods used in this brief

• Inquiry Circle
• Gallery Walk
• Think-Pair-Share