Exothermic Reactions

Active learning works for exothermic reactions because students need to feel the heat release firsthand and see the energy transfer in action. Watching temperature rise or sketching reaction profiles makes abstract energy changes concrete and memorable.

• Year 10
• Chemistry
• 4 activities
• 20 min–40 min

Learning Objectives

1. Explain the energy transfer occurring in exothermic reactions, relating it to a temperature increase in the surroundings.
2. Analyze reaction profiles to differentiate the energy levels of reactants and products in exothermic processes.
3. Identify and classify common exothermic reactions based on observable temperature changes.
4. Compare the energy released in different exothermic reactions using provided data or reaction profiles.

Inquiry Circle

⏱ 35 min·Pairs

Pairs: Temperature Logging Practical

Pairs dissolve calcium chloride in water or react magnesium ribbon with dilute acid, using digital thermometers to log initial and peak temperatures every 30 seconds. They calculate temperature change and plot line graphs. Discuss why energy releases as heat.

Prepare & details

Explain why exothermic reactions cause the surroundings to heat up.

Facilitation Tip: During Temperature Logging Practical, circulate with a timer and remind pairs to record both temperature and time at precise intervals to build reliable data.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 30 min·Small Groups

Small Groups: Reaction Profile Workshop

Provide printed energy level data for exothermic reactions. Groups sketch profiles, mark activation energy barrier and negative delta H. Compare profiles with endothermic examples and present to class.

Prepare & details

Analyze everyday examples of exothermic reactions and their applications.

Facilitation Tip: In the Reaction Profile Workshop, provide grid paper and coloured pencils so groups can clearly mark the energy drop and label axes before peer review.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 40 min·Whole Class

Whole Class: Demo and Prediction Cycle

Teacher activates a hand warmer; class predicts temperature outcome first. Observe changes with shared thermometer, then analyse via reaction profile on board. Link to respiration or fuel burning.

Prepare & details

Differentiate between the energy of reactants and products in an exothermic reaction using reaction profiles.

Facilitation Tip: For the Demo and Prediction Cycle, pause after the reaction to ask students to compare their predictions to what they see, reinforcing cause and effect.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 20 min·Individual

Individual: Application Spotter

Students review images of scenarios like compost heaps or fireworks. Note exothermic features, sketch mini-profiles, and note applications. Share top examples in pairs.

Prepare & details

Explain why exothermic reactions cause the surroundings to heat up.

Facilitation Tip: During Application Spotter, circulate and prompt students to justify their choices with evidence from the activity or prior knowledge.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Teaching This Topic

Teachers approach this topic by building from observable phenomena—temperature change—into abstract energy diagrams. Avoid rushing to the reaction profile before students have felt the heat; let the practical anchor the concept. Research shows students grasp energy changes best when they first measure temperature rises, then translate that into a profile with peer feedback. Keep the focus on energy transfer, not just labels, and revisit misconceptions explicitly during discussion.

What to Expect

Successful learning looks like students confidently linking temperature increases to energy release, accurately sketching reaction profiles with energy drops, and applying the concept to everyday examples. They should explain why surroundings heat up and not just memorise combustion as the only exothermic reaction.

Watch Out for These Misconceptions

Common Misconception

During Temperature Logging Practical, watch for students attributing temperature rises to the surroundings absorbing heat rather than the reaction releasing it.

What to Teach Instead

Have pairs note that the reaction mixture itself is heating up, which they will feel when touching the container, and ask them to explain where the energy comes from using their data.

Common Misconception

During Reaction Profile Workshop, watch for students drawing flat or ascending lines between reactants and products.

What to Teach Instead

Ask groups to compare their sketches with a correct model on the board, then revise their lines to show a clear drop in energy, explaining the reason for the change.

Common Misconception

During Application Spotter, watch for students limiting exothermic reactions to combustion only.

What to Teach Instead

Prompt students to justify their choices with examples from neutralisation or dissolving processes, and ask them to add two more non-combustion examples to their lists.

Assessment Ideas

Quick Check

After Application Spotter, ask students to circle the exothermic reactions from a list and explain why one example is exothermic, collecting their responses to check for accurate use of energy release and temperature changes.

Discussion Prompt

After Demo and Prediction Cycle, pose the question: 'If an exothermic reaction releases energy, why does the reaction mixture itself feel hot, while the surroundings also heat up?' Listen for students discussing energy transfer pathways and the definition of surroundings.

Exit Ticket

During Reaction Profile Workshop, provide students with a simple reaction profile diagram to label reactants, products, and energy released, and ask them to describe in one sentence what the diagram shows about energy change.

Extensions & Scaffolding

• Challenge: Ask students to design a poster explaining how hand warmers use exothermic reactions, including reaction equations and energy profiles.
• Scaffolding: Provide a partially completed reaction profile template for students who struggle to start, with key points like reactants and products already labelled.
• Deeper exploration: Have students research and compare the energy released per gram in different exothermic reactions, such as combustion of fuels and neutralisation of acids.

Key Vocabulary

Exothermic Reaction	A chemical reaction that releases energy, usually in the form of heat, into its surroundings.
Reaction Profile	A graph that shows the change in energy during a chemical reaction, illustrating the energy of reactants, products, and the activation energy.
Activation Energy	The minimum amount of energy required for reactants to overcome the energy barrier and initiate a chemical reaction.
Energy Release	The net transfer of energy from the chemical system to the surroundings during an exothermic reaction.