Chemistry · Year 12

Active learning ideas

Bronsted-Lowry Acids and Bases

Active learning works for this topic because students need to visualize proton transfer, not just memorize definitions. Moving from static diagrams to dynamic role play and matching games helps them internalize the shifting identities of acids and bases during reactions.

• ACARA Content Descriptions
• ACSCH099

• 15–25 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Role Play
• 20 min · Whole Class

Role Play: The Proton Handover

Students act as different molecules (e.g., HCl, H2O, NH3). One student holds a 'proton' (a ball) and must decide, based on their molecular identity, whether to donate it to another student, identifying the resulting conjugate pairs in the process.

Differentiate between Arrhenius and Bronsted-Lowry definitions of acids and bases.

Facilitation Tip

During the Role Play, assign clear roles for H+ donors and acceptors, and require students to physically move between sides of the room as protons transfer to reinforce the direction of reactions.

What to look for

Present students with the reaction: NH3(aq) + H2O(l) <=> NH4+(aq) + OH-(aq). Ask them to identify the Bronsted-Lowry acid, base, conjugate acid, and conjugate base in this reaction.

• Apply
• Analyze
• Evaluate
• Social Awareness
• Self-Awareness

Activity 02

• Think-Pair-Share
• 15 min · Pairs

Think-Pair-Share: Amphiprotic Detectives

Pairs are given a list of ions like HCO3- and HPO42-. They must write two equations for each: one where it acts as an acid and one as a base, then share their reasoning with another pair to verify the conjugate pairs formed.

Identify conjugate acid-base pairs in various chemical reactions.

Facilitation Tip

During the Think-Pair-Share, provide molecular diagrams with ionisable hydrogens highlighted so students can focus on bond polarity rather than guessing.

What to look for

Provide students with two chemical equations. For each equation, ask them to circle the conjugate acid-base pairs and label each species as either an acid or a base according to the Bronsted-Lowry definition.

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

Activity 03

• Gallery Walk
• 25 min · Small Groups

Gallery Walk: Conjugate Matching

Cards with various acids and bases are posted around the room. Students move in small groups to find and record the matching conjugate partner for each card, explaining the 'one proton difference' rule to their peers.

Explain why some substances can act as both an acid and a base (amphiprotic).

Facilitation Tip

During the Gallery Walk, post reaction equations at different stations and have students physically match conjugate pairs using sticky notes to make abstract pairs concrete.

What to look for

Pose the question: 'Why is the Bronsted-Lowry definition more useful than the Arrhenius definition for understanding reactions in non-aqueous solvents like liquid ammonia?' Facilitate a class discussion where students share their reasoning.

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

A few notes on teaching this unit

Start by explicitly linking the new model to Year 10 Arrhenius knowledge to avoid a disconnect. Use analogies like a ‘hot potato’ game for proton transfer, but transition quickly to chemical equations so students practice identifying roles. Avoid overemphasizing memorization of examples; instead, prioritize repeated practice with unfamiliar acids and bases to build flexible understanding.

Successful learning looks like students confidently identifying acids, bases, conjugate pairs, and amphiprotic substances in new equations without prompting. They should also explain why proton transfer defines these roles, not molecular composition alone.

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Watch Out for These Misconceptions

• During the Role Play activity, watch for students who treat all hydrogens as acidic. Redirect them by asking them to examine molecular structures and identify which hydrogen is bonded to an electronegative atom (e.g., oxygen or nitrogen) that can stabilize the negative charge after donation.

  During the Think-Pair-Share activity, provide a card with methane (CH4) and a card with hydrogen chloride (HCl). Ask students to compare the polarity of the bonds and explain why only HCl can donate a proton. Use their discussion to clarify that only ionisable hydrogens in polar bonds act as Bronsted-Lowry acids.

• During the Gallery Walk activity, watch for students who pair conjugate acids and bases by counting total hydrogens rather than tracking single proton differences.

  During the Gallery Walk activity, hand out a checklist that asks students to record the proton count for each species in the reaction and verify that conjugate pairs differ by exactly one proton. Circulate and prompt groups to explain their reasoning using the checklist.

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Methods used in this brief

• Role Play
• Think-Pair-Share
• Gallery Walk