Mathematics · Year 2

Active learning ideas

Comparing and Ordering Mass (Informal Units)

Active, hands-on tasks let Year 2 students feel mass differences directly and test predictions safely. Moving, balancing, and discussing build accurate language and mental models that static worksheets cannot.

• ACARA Content Descriptions
• AC9M2M01

• 20–40 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Stations Rotation
• 40 min · Small Groups

Stations Rotation: Balance Comparisons

Prepare four stations with object pairs like books and erasers. Students predict which is heavier, test on a balance scale, record with drawings and labels, then switch stations. End with a class share of surprises.

How can we tell if one object is heavier than another without using a scale?

Facilitation Tip

During Station Rotation: Balance Comparisons, place identical balance scales at each station and demonstrate how to zero the pans before adding objects to ensure fair tests.

What to look for

Provide students with two distinct classroom objects (e.g., a book and a pencil). Ask: 'Which object do you think is heavier? How can you test your idea without a scale?' Observe their methods and listen to their reasoning.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Activity 02

• Plan-Do-Review
• 25 min · Pairs

Pairs: Informal Unit Balances

Pair students to compare classroom items using hands or linking cubes as units. They balance one side against units on the other, note heavier or lighter, and create a class mass ladder. Discuss fair testing rules first.

Explain why using a balance scale helps us compare the mass of two objects accurately.

Facilitation Tip

In Pairs: Informal Unit Balances, give one set of objects to each pair and one bag of blocks so they must negotiate measurement and recording together.

What to look for

Give each student a small bag containing three objects of varying mass. Ask them to draw the objects in order from lightest to heaviest on their ticket and write one sentence explaining their order.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

Activity 03

• Plan-Do-Review
• 35 min · Whole Class

Whole Class: Prediction Relay

Line up 10 classroom objects. Teams predict order from lightest to heaviest, test sequentially with a balance, adjust as needed. Tally correct predictions and reflect on strategies.

Predict which objects in the classroom are heavier or lighter than a given item.

Facilitation Tip

During the Prediction Relay, set a timer for 20 seconds so students make quick predictions and then immediately test them, reinforcing the link between prediction and evidence.

What to look for

Present a balance scale with two different objects. Ask: 'What does it mean if this side of the scale is lower than the other? How does this help us compare the mass of the objects?'

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

Activity 04

• Plan-Do-Review
• 20 min · Individual

Individual: Mass Hunt Journal

Students select five personal items, predict relative masses, test with a partner balance, and journal orders with sketches. Share one insight with the class.

How can we tell if one object is heavier than another without using a scale?

Facilitation Tip

In the Mass Hunt Journal, model how to draw a simple table with columns for object, prediction, and outcome to scaffold recording.

What to look for

Provide students with two distinct classroom objects (e.g., a book and a pencil). Ask: 'Which object do you think is heavier? How can you test your idea without a scale?' Observe their methods and listen to their reasoning.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

A few notes on teaching this unit

Teachers guide students to focus on the balance scale as a tool for evidence rather than appearance. Avoid rushing to formal units; let children experience the idea of equal mass through repeated balancing. Research shows that multiple short, concrete trials spaced over days strengthen retention of mass concepts more than single demonstrations.

By the end of the sequence, students will confidently order three objects by mass, explain the role of a balance scale, and use informal units to justify comparisons. They will also revise initial ideas when evidence contradicts them.

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Watch Out for These Misconceptions

• During Station Rotation: Balance Comparisons, watch for students who declare one object heavier simply because it is bigger or smaller.

  Have them place both objects on the scale and read the tilt together. Ask, 'Does size tell us about mass here? What does the scale show?' Record findings on a class chart so students revise their initial ideas with evidence.

• During Pairs: Informal Unit Balances, watch for children who assume every object must balance with an exact number of blocks.

  Challenge pairs to find a third object that balances with the same number of blocks as one of their original objects. Discuss why different objects can have the same mass.

• During the Mass Hunt Journal, watch for students who confuse the position of the scale with the mass of the object.

  Return to the journal entry and ask them to circle the side that went down and label it 'heavier'. Repeat with a second entry to build the habit of linking tilt direction to mass.

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Methods used in this brief

• Stations Rotation
• Plan-Do-Review