Endothermic Reactions

Active learning works well here because students need to feel the temperature drop with their own hands and see the data change in real time. Watching a reaction cool down while holding a beaker makes the abstract concept of energy transfer concrete and memorable.

• Year 10
• Chemistry
• 4 activities
• 20 min–45 min

Learning Objectives

1. Explain why endothermic reactions cause a decrease in the temperature of their surroundings.
2. Analyze everyday applications of endothermic reactions, such as in sports injury packs.
3. Differentiate between the energy levels of reactants and products in endothermic reactions using reaction profile diagrams.
4. Classify reactions as endothermic based on observed temperature changes.

Inquiry Circle

⏱ 30 min·Pairs

Demonstration Pairs: Salt Dissolutions

Pairs test three salts (ammonium nitrate, potassium chloride, sodium chloride) by dissolving equal masses in water and recording temperature changes every 30 seconds with digital thermometers. They graph results and classify each as endothermic or not. Discuss which bonds might explain the energy absorption.

Prepare & details

Explain why endothermic reactions cause the surroundings to cool down.

Facilitation Tip: During Demonstration Pairs, circulate with a wireless thermometer so every pair sees the temperature trend simultaneously on the projector.

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

⏱ 35 min·Small Groups

Small Groups: Reaction Profile Builds

Groups use foam blocks or Lego to represent energy levels, stacking higher for products in endothermic profiles versus lower for exothermic. Add labels for activation energy and compare with class sketches. Vote on most accurate models.

Prepare & details

Analyze everyday examples of endothermic reactions and their applications.

Facilitation Tip: In Small Groups, provide pre-cut reaction profiles so students focus on matching energy flow arrows rather than drawing from scratch.

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

⏱ 45 min·Whole Class

Whole Class: Everyday Hunt and Demo

Students list five potential endothermic examples from home or school, then class votes and tests two safe ones like vinegar-baking soda variants or hand warmer reversals. Log temperatures and link to profiles on shared board.

Prepare & details

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

Facilitation Tip: For the Everyday Hunt, require students to bring one photo and one short explanation to avoid generic answers like ‘freezer’ or ‘ice pack’.

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: Profile Matching Cards

Each student matches cards showing reactions, temperature graphs, and profiles to endothermic or exothermic categories. Swap and check peers' work, then justify one match with energy terms.

Prepare & details

Explain why endothermic reactions cause the surroundings to cool down.

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

Start with a dramatic visible demo, such as ammonium nitrate dissolving in water inside a foam cup, to create surprise and curiosity. Avoid long lectures about bond energies until students have firsthand data; research shows conceptual change happens after concrete experience, not before. Use the language of ‘energy in’ and ‘energy out’ consistently so students link the profile graphs directly to what they felt.

What to Expect

Students will confidently explain why endothermic reactions cool their surroundings and accurately sketch energy profiles that show reactants below products. They will also distinguish endothermic from exothermic dissolving salts by interpreting their own thermometer readings.

Watch Out for These Misconceptions

Common Misconception

During Demonstration Pairs: Salt Dissolutions, watch for students attributing the cooling to the salt ‘taking in cold’ instead of the mixture absorbing heat.

What to Teach Instead

Prompt students to read thermometer values aloud every 30 seconds and verbally connect each drop to their energy profile arrows, reinforcing that energy is moving from the surroundings into the reaction.

Common Misconception

During Small Groups: Reaction Profile Builds, watch for students drawing the product line below the reactant line.

What to Teach Instead

Have groups exchange profiles and annotate with sticky notes where they think energy enters, forcing them to confront and correct the profile based on their Demonstration Pairs data.

Common Misconception

During Everyday Hunt and Demo, watch for students labeling all dissolving salts as endothermic.

What to Teach Instead

Set up station rotations with sodium hydroxide and calcium chloride as contrasting salts; students must present their thermometer readings on a whiteboard before justifying their classification in a gallery walk.

Assessment Ideas

Quick Check

After Demonstration Pairs, give students a two-column list of reactions including dissolving ammonium nitrate and burning wood. Ask them to place a tick or cross and write one sentence explaining their choice based on temperature change.

Exit Ticket

After Reaction Profile Builds, collect their labeled profiles and have them write one sentence explaining why the surroundings cool, using the words ‘energy absorbed’ and ‘products higher than reactants’.

Discussion Prompt

During the Everyday Hunt and Demo, ask students to share their cold pack designs in small groups and challenge peers to suggest improvements based on endothermic reaction duration and safety.

Extensions & Scaffolding

• Challenge: Ask students to design a two-salt cold pack that maintains 10 °C for 20 minutes using their profile data.
• Scaffolding: Provide a word bank and sentence stems for the exit ticket profile to support students with weak literacy or EAL needs.
• Deeper: Have students calculate the approximate energy absorbed using q = m c ΔT and compare to bond-energy values in data books.

Key Vocabulary

Endothermic Reaction	A chemical reaction that absorbs thermal energy from its surroundings, causing the temperature of the surroundings to decrease.
Energy Absorption	The process where a system takes in energy, often in the form of heat, from its environment.
Temperature Decrease	A reduction in the hotness or coldness of a substance or its surroundings, often measured with a thermometer.
Reaction Profile	A graph that shows the change in energy during a chemical reaction, plotting energy against the reaction pathway.