Comparing by Weight

Overview

Unit Title: Measuring Mass Fun!
Lesson Number: 5 of 6
Lesson Title: Comparing Masses
Duration: 30 minutes
Year Level: Year 2
Class Size: 9 students
Curriculum Area: Mathematics and Statistics
Strand: Measurement
Achievement Objective – Level 1 (NZ Curriculum):
“Compare and order objects by length, area, volume and mass.”
(Ministry of Education - New Zealand Curriculum Level 1)

This playful, hands-on lesson is designed to help tamariki understand the concept of comparing mass. By working in small groups with everyday classroom items, students will explore the language of mass (heavier/lighter) and make judgements based on estimation and comparison—not just through digital scales, but via physical handling and collaborative discussion. This supports the development of early mathematical thinking in measurement and builds foundational skills that connect maths to real-life contexts.

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Learning Intentions

Students will:

• Understand that mass describes how heavy or light something is.
• Use everyday language to compare the mass of objects (e.g. "This is heavier than that").
• Work together to sort and talk about different objects based on their mass.

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Success Criteria

Students can:

• Correctly use words like heavier, lighter, and about the same to describe mass.
• Confidently compare two or more items by hand and explain their judgement.
• Work with a group to sort a small set of items in order of mass.

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Key Vocabulary

• Mass
• Heavier
• Lighter
• Same weight
• Compare

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Resources Needed

• Comparison charts: Laminated A3 sheets with columns labelled Lighter than, Heavier than, Same as (provided for each group).
• Assorted classroom items: Examples include a sponge, small rock, glue stick, pencil case, soft toy, small book, unifix cube tower, lunchbox, empty water bottle, rubik’s cube etc. (Each group to receive a set of 6–8 items).
• 1 balance scale: To demonstrate, not necessarily for use in each group.
• Sorting cards: Picture cards of objects (optional extension or support).
• Small felt mats or trays to group objects into categories.
• Sticky notes: For students to label categories as a plenary.

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Lesson Structure

⏰ 5 mins – Warm-up / Introduction

Whole Class on the Mat

1. Begin with a quick revisit of what "mass" means. Use real objects to refresh key terms (heavier, lighter).
2. Pass around two dramatically different items (e.g. soft toy and rock) and ask:
   “Which one feels heavier? Why? How do you know?”
3. Prompt students to describe how they feel the difference – introduce the idea that we can compare without needing a scale.

Teacher Talk Tip: Use te reo Māori where appropriate:
"He aha te mea taumaha ake?" (Which is heavier?)
"He aha te mea māmā ake?" (Which is lighter?)

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⏰ 15 mins – Main Activity: Group Sorting Carousel

In Groups of 3 (3 Groups Total)

Each group receives a tray/basket of assorted objects and a laminated comparison chart.

Instructions:

1. Choose one anchor object from your set (e.g. the glue stick).

2. Compare every other object to the anchor, using your hands to feel the difference.

3. Place each object into one of the chart columns based on comparison with the anchor:

   • Lighter than
   • Same as (or very close)
   • Heavier than

4. Once done, pick a new anchor and repeat!

5. Encourage ākonga to talk out loud:

   • “The pencil case is heavier because it has more inside.”
   • “This sponge is lighter—it’s full of air and squishy!”

Teacher role: Float between groups, ask probing questions like:

• “What makes that one feel heavier?”
• “Do you all agree on this? Why/why not?”
• “What if we had a scale—do you think it would say the same?”

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⏰ 5 mins – Whole-Class Discussion

Bring the class back to the mat. Invite 2–3 students to share:

• Something surprising they discovered
• Items they found tricky to compare

Use a balance scale to check one or two disputed comparisons as a class.

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⏰5 mins – Wrap-Up Reflection

Mini Plenary on the Mat

1. Recap language learnt today: heavier, lighter, same as
2. On sticky notes, students label one object from earlier with a mass comparison sentence.
   Example: "My lunchbox is heavier than the glue stick."
3. Create a quick wall display of their sticky notes under headings: Heavier than..., Lighter than...

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Differentiation & Support

• Extension: Include picture cards of surprising object weights (feather, brick, balloon, lemon) and ask “Which would be heavier?” to encourage estimation.
• Scaffolding: Students with language needs can use sentence starters:
  • "I think the ___ is heavier than the ___."
  • "These feel the same because…"
• Inclusion: Use tactile-friendly, safe items that are easy to manipulate.

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Links to Key Competencies

• Thinking: Making comparisons through internal reasoning
• Managing self: Respecting turn-taking and group roles
• Relating to others: Sharing reasoning, collaborative decision-making
• Using language, symbols and texts: Using comparative mathematical vocabulary
• Participating and contributing: Engaging actively in group inquiry

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Assessment for Learning (AfL)

Formative Observations:

• Listen for accurate vocabulary use during group work and discussion
• Watch for logical placement in sorting activity
• Scaffold where needed—but encourage independent explanation

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Teacher Reflection Prompts (Post-Lesson)

• Were students able to justify their comparisons confidently?
• Did certain items confuse students? Why?
• How can I better support those still struggling with basic comparison terms?

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Next Lesson Preview

Lesson 6: Estimating and Checking Mass
Tamariki will estimate the mass of objects and check using classroom balance scales. This will consolidate vocabulary and concepts explored in the previous five lessons.

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Ngā mihi for supporting the mathematical development of your tamariki in such practical, playful ways! ✨